Anatomy_Gray

Anatomy_Gray. Roof of popliteal fossa The roof of the popliteal fossa is covered by superficial fascia and skin (Fig. 6.83C). The most important structure in the superficial fascia is the small saphenous vein. This vessel ascends vertically in the superficial fascia on the back of the leg from the lateral side of the dorsal venous arch in the foot. It ascends to the back of the knee where it penetrates deep fascia, which forms the roof of the popliteal fossa, and joins with the popliteal vein. One other structure that passes through the roof of the fossa is the posterior cutaneous nerve of the thigh, which descends through the thigh superficial to the hamstring muscles, passes through the roof of the popliteal fossa, and then continues inferiorly with the small saphenous vein to innervate skin on the upper half of the back of the leg. The leg is that part of the lower limb between the knee joint and ankle joint (Fig. 6.84):


Anatomy_Gray

Anatomy_Gray. The leg is that part of the lower limb between the knee joint and ankle joint (Fig. 6.84): Proximally, most major structures pass between the thigh and leg through or in relation to the popliteal fossa behind the knee. Distally, structures pass between the leg and foot mainly through the tarsal tunnel on the posteromedial side of the ankle, the exceptions being the anterior tibial artery and the ends of the deep and superficial fibular nerves, which enter the foot anterior to the ankle. The bony framework of the leg consists of two bones, the tibia and fibula, arranged in parallel. The fibula is much smaller than the tibia and is on the lateral side of the leg. It articulates superiorly with the inferior aspect of the lateral condyle of the proximal tibia, but does not take part in formation of the knee joint. The distal end of the fibula is firmly anchored to the tibia by a fibrous joint and forms the lateral malleolus of the ankle joint.


Anatomy_Gray

Anatomy_Gray. The tibia is the weight-bearing bone of the leg and is therefore much larger than the fibula. Above, it takes part in the formation of the knee joint and below it forms the medial malleolus and most of the bony surface for articulation of the leg with the foot at the ankle joint. The leg is divided into anterior (extensor), posterior (flexor), and lateral (fibular) compartments by: an interosseous membrane, which links adjacent borders of the tibia and fibula along most of their length; two intermuscular septa, which pass between the fibula and deep fascia surrounding the limb; and direct attachment of the deep fascia to the periosteum of the anterior and medial borders of the tibia (Fig. 6.84).


Anatomy_Gray

Anatomy_Gray. Muscles in the anterior compartment of the leg dorsiflex the ankle, extend the toes, and invert the foot. Muscles in the posterior compartment plantarflex the ankle, flex the toes, and invert the foot. Muscles in the lateral compartment evert the foot. Major nerves and vessels supply or pass through each compartment. Shaft and distal end of tibia The shaft of the tibia is triangular in cross section and has anterior, interosseous, and medial borders and medial, lateral, and posterior surfaces (Fig. 6.85): The anterior and medial borders and the entire medial surface are subcutaneous and easily palpable. The interosseous border of the tibia is connected, by the interosseous membrane, along its length to the interosseous border of the fibula. The posterior surface is marked by an oblique line (the soleal line).


Anatomy_Gray

Anatomy_Gray. The posterior surface is marked by an oblique line (the soleal line). The soleal line descends across the bone from the lateral side to the medial side where it merges with the medial border. In addition, a vertical line descends down the upper part of the posterior surface from the midpoint of the soleal line. It disappears in the lower one-third of the tibia. The shaft of the tibia expands at both the upper and lower ends to support the body’s weight at the knee and ankle joints. The distal end of the tibia is shaped like a rectangular box with a bony protuberance on the medial side (the medial malleolus; Fig. 6.81). The upper part of the box is continuous with the shaft of the tibia while the lower surface and the medial malleolus articulate with one of the tarsal bones (talus) to form a large part of the ankle joint.


Anatomy_Gray

Anatomy_Gray. The posterior surface of the box-like distal end of the tibia is marked by a vertical groove, which continues inferiorly and medially onto the posterior surface of the medial malleolus. The groove is for the tendon of the tibialis posterior muscle. The lateral surface of the distal end of the tibia is occupied by a deep triangular notch (the fibular notch), to which the distal head of the fibula is anchored by a thickened part of the interosseous membrane. Shaft and distal end of fibula The fibula is not involved in weight-bearing. The fibular shaft is therefore much narrower than the shaft of the tibia. Also, and except for the ends, the fibula is enclosed by muscles.


Anatomy_Gray

Anatomy_Gray. The fibula is not involved in weight-bearing. The fibular shaft is therefore much narrower than the shaft of the tibia. Also, and except for the ends, the fibula is enclosed by muscles. Like the tibia, the shaft of the fibula is triangular in cross section and has three borders and three surfaces for the attachment of muscles, intermuscular septa, and ligaments (Fig. 6.85). The interosseous border of the fibula faces and is attached to the interosseous border of the tibia by the interosseous membrane. Intermuscular septa attach to the anterior and posterior borders. Muscles attach to the three surfaces. The narrow medial surface faces the anterior compartment of the leg, the lateral surface faces the lateral compartment of the leg, and the posterior surface faces the posterior compartment of the leg. The posterior surface is marked by a vertical crest (medial crest), which divides the posterior surface into two parts each attached to a different deep flexor muscle.


Anatomy_Gray

Anatomy_Gray. The posterior surface is marked by a vertical crest (medial crest), which divides the posterior surface into two parts each attached to a different deep flexor muscle. The distal end of the fibula expands to form the spade-shaped lateral malleolus (Fig. 6.85). The medial surface of the lateral malleolus bears a facet for articulation with the lateral surface of the talus, thereby forming the lateral part of the ankle joint. Just superior to this articular facet is a triangular area, which fits into the fibular notch on the distal end of the tibia. Here the tibia and fibula are joined together by the distal end of the interosseous membrane. Posteroinferior to the facet for articulation with the talus is a pit or fossa (the malleolar fossa) for the attachment of the posterior talofibular ligament associated with the ankle joint. The posterior surface of the lateral malleolus is marked by a shallow groove for the tendons of the fibularis longus and fibularis brevis muscles.


Anatomy_Gray

Anatomy_Gray. The posterior surface of the lateral malleolus is marked by a shallow groove for the tendons of the fibularis longus and fibularis brevis muscles. Interosseous membrane of leg The interosseous membrane of the leg is a tough fibrous sheet of connective tissue that spans the distance between facing interosseous borders of the tibial and fibular shafts (Fig. 6.86). The collagen fibers descend obliquely from the interosseous border of the tibia to the interosseous border of the fibula, except superiorly where there is a ligamentous band, which ascends from the tibia to fibula. There are two apertures in the interosseous membrane, one at the top and the other at the bottom, for vessels to pass between the anterior and posterior compartments of the leg. The interosseous membrane not only links the tibia and fibula together, but also provides an increased surface area for muscle attachment.


Anatomy_Gray

Anatomy_Gray. The interosseous membrane not only links the tibia and fibula together, but also provides an increased surface area for muscle attachment. The distal ends of the fibula and tibia are held together by the inferior aspect of the interosseous membrane, which spans the narrow space between the fibular notch on the lateral surface of the distal end of the tibia and the corresponding surface on the distal end of the fibula. This expanded end of the interosseous membrane is reinforced by anterior and posterior tibiofibular ligaments. This firm linking together of the distal ends of the tibia and fibula is essential to produce the skeletal framework for articulation with the foot at the ankle joint. Posterior compartment of leg


Anatomy_Gray

Anatomy_Gray. Posterior compartment of leg Muscles in the posterior (flexor) compartment of the leg are organized into two groups, superficial and deep, separated by a layer of deep fascia. Generally, the muscles mainly plantarflex and invert the foot and flex the toes. All are innervated by the tibial nerve. The superficial group of muscles in the posterior compartment of the leg comprises three muscles—the gastrocnemius, plantaris, and soleus (Table 6.6)—all of which insert onto the heel (calcaneus) of the foot and plantarflex the foot at the ankle joint (Fig. 6.87). As a unit, these muscles are large and powerful because they propel the body forward off the planted foot during walking and can elevate the body upward onto the toes when standing. Two of the muscles (gastrocnemius and plantaris) originate on the distal end of the femur and can also flex the knee.


Anatomy_Gray

Anatomy_Gray. The gastrocnemius muscle is the most superficial of the muscles in the posterior compartment and is one of the largest muscles in the leg (Fig. 6.87). It originates from two heads, one lateral and one medial: The medial head is attached to an elongate roughening on the posterior aspect of the distal femur just behind the adductor tubercle and above the articular surface of the medial condyle. The lateral head originates from a distinct facet on the upper lateral surface of the lateral femoral condyle where it joins the lateral supracondylar line. At the knee, the facing margins of the two heads of the gastrocnemius form the lateral and medial borders of the lower end of the popliteal fossa. In the upper leg, the heads of the gastrocnemius combine to form a single elongate muscle belly, which forms much of the soft tissue bulge identified as the calf.


Anatomy_Gray

Anatomy_Gray. In the upper leg, the heads of the gastrocnemius combine to form a single elongate muscle belly, which forms much of the soft tissue bulge identified as the calf. In the lower leg, the muscle fibers of the gastrocnemius converge with those of the deeper soleus muscle to form the calcaneal tendon, which attaches to the calcaneus (heel) of the foot. The gastrocnemius plantarflexes the foot at the ankle joint and can also flex the leg at the knee joint. It is innervated by the tibial nerve. The plantaris has a small muscle belly proximally and a long thin tendon, which descends through the leg and joins the calcaneal tendon (Fig. 6.87). The muscle takes origin superiorly from the lower part of the lateral supracondylar ridge of the femur and from the oblique popliteal ligament associated with the knee joint.


Anatomy_Gray

Anatomy_Gray. The short spindle-shaped muscle body of the plantaris descends medially, deep to the lateral head of the gastrocnemius, and forms a thin tendon, which passes between the gastrocnemius and soleus muscles and eventually fuses with the medial side of the calcaneal tendon near its attachment to the calcaneus. The plantaris contributes to plantarflexion of the foot at the ankle joint and flexion of the leg at the knee joint, and is innervated by the tibial nerve. The soleus is a large flat muscle under the gastrocnemius muscle (Fig. 6.87). It is attached to the proximal ends of the fibula and tibia, and to a tendinous ligament, which spans the distance between the two heads of attachment to the fibula and tibia: On the proximal end of the fibula, the soleus originates from the posterior aspect of the head and adjacent surface of the neck and upper shaft of the fibula. On the tibia, the soleus originates from the soleal line and adjacent medial border.


Anatomy_Gray

Anatomy_Gray. On the tibia, the soleus originates from the soleal line and adjacent medial border. The ligament, which spans the distance between the attachments to the tibia and fibula, arches over the popliteal vessels and tibial nerve as they pass from the popliteal fossa into the deep region of the posterior compartment of the leg. In the lower leg, the soleus muscle narrows to join the calcaneal tendon that attaches to the calcaneus. The soleus muscle, together with the gastrocnemius and plantaris, plantarflexes the foot at the ankle joint. It is innervated by the tibial nerve. There are four muscles in the deep posterior compartment of the leg (Fig. 6.88)—the popliteus, flexor hallucis longus, flexor digitorum longus, and tibialis posterior (Table 6.7). The popliteus muscle acts on the knee, whereas the other three muscles act mainly on the foot.


Anatomy_Gray

Anatomy_Gray. The popliteus is the smallest and most superior of the deep muscles in the posterior compartment of the leg. It unlocks the extended knee at the initiation of flexion and stabilizes the knee by resisting lateral (external) rotation of the tibia on the femur. It is flat and triangular in shape, forms part of the floor of the popliteal fossa (Fig. 6.88), and is inserted into a broad triangular region above the soleal line on the posterior surface of the tibia. The popliteus muscle ascends laterally across the lower aspect of the knee and originates from a tendon, which penetrates the fibrous membrane of the joint capsule of the knee. The tendon ascends laterally around the joint where it passes between the lateral meniscus and the fibrous membrane and then into a groove on the inferolateral aspect of the lateral femoral condyle. The tendon attaches to and originates from a depression at the anterior end of the groove.


Anatomy_Gray

Anatomy_Gray. When initiating gait from a standing position, contraction of the popliteus laterally rotates the femur on the fixed tibia, unlocking the knee joint. The popliteus muscle is innervated by the tibial nerve. The flexor hallucis longus muscle originates on the lateral side of the posterior compartment of the leg and inserts into the plantar surface of the great toe on the medial side of the foot (Fig. 6.88). It arises mainly from the lower two-thirds of the posterior surface of the fibula and adjacent interosseous membrane.


Anatomy_Gray

Anatomy_Gray. The muscle fibers of the flexor hallucis longus converge inferiorly to form a large cord-like tendon, which passes behind the distal head of the tibia and then slips into a distinct groove on the posterior surface of the adjacent tarsal bone (talus) of the foot. The tendon curves anteriorly first under the talus and then under a shelf of bone (the sustentaculum tali), which projects medially from the calcaneus, and then continues anteriorly through the sole of the foot to insert on the inferior surface of the base of the distal phalanx of the great toe. The flexor hallucis longus flexes the great toe. It is particularly active during the toe-off phase of walking when the body is propelled forward off the stance leg and the great toe is the last part of the foot to leave the ground. It can also contribute to plantarflexion of the foot at the ankle joint and is innervated by the tibial nerve.


Anatomy_Gray

Anatomy_Gray. The flexor digitorum longus muscle originates on the medial side of the posterior compartment of the leg and inserts into the lateral four digits of the foot (Fig. 6.88). It arises mainly from the medial side of the posterior surface of the tibia inferior to the soleal line. The flexor digitorum longus descends in the leg and forms a tendon, which crosses posterior to the tendon of the tibialis posterior muscle near the ankle joint. The tendon continues inferiorly in a shallow groove behind the medial malleolus and then swings forward to enter the sole of the foot. It crosses inferior to the tendon of the flexor hallucis longus muscle to reach the medial side of the foot and then divides into four tendons, which insert on the plantar surfaces of the bases of the distal phalanges of digits II to V.


Anatomy_Gray

Anatomy_Gray. The flexor digitorum longus flexes the lateral four toes. It is involved with gripping the ground during walking and propelling the body forward off the toes at the end of the stance phase of gait. It is innervated by the tibial nerve. The tibialis posterior muscle originates from the interosseous membrane and the adjacent posterior surfaces of the tibia and fibula (Fig. 6.88). It lies between and is overlapped by the flexor digitorum longus and the flexor hallucis longus muscles.


Anatomy_Gray

Anatomy_Gray. Near the ankle, the tendon of the tibialis posterior is crossed superficially by the tendon of the flexor digitorum longus muscle and lies medial to this tendon in the groove on the posterior surface of the medial malleolus. The tendon curves forward under the medial malleolus and enters the medial side of the foot. It wraps around the medial margin of the foot to attach to the plantar surfaces of the medial tarsal bones, mainly to the tuberosity of the navicular and to the adjacent region of the medial cuneiform. The tibialis posterior inverts and plantarflexes the foot, and supports the medial arch of the foot during walking. It is innervated by the tibial nerve. The popliteal artery is the major blood supply to the leg and foot and enters the posterior compartment of the leg from the popliteal fossa behind the knee (Fig. 6.89).


Anatomy_Gray

Anatomy_Gray. The popliteal artery is the major blood supply to the leg and foot and enters the posterior compartment of the leg from the popliteal fossa behind the knee (Fig. 6.89). The popliteal artery passes into the posterior compartment of the leg between the gastrocnemius and popliteus muscles. As it continues inferiorly it passes under the tendinous arch formed between the fibular and tibial heads of the soleus muscle and enters the deep region of the posterior compartment of the leg where it immediately divides into an anterior tibial artery and a posterior tibial artery. Two large sural arteries, one on each side, branch from the popliteal artery to supply the gastrocnemius, soleus, and plantaris muscles (Fig. 6.89). In addition, the popliteal artery gives rise to branches that contribute to a collateral network of vessels around the knee joint (see Fig. 6.80).


Anatomy_Gray

Anatomy_Gray. The anterior tibial artery passes forward through the aperture in the upper part of the interosseous membrane and enters and supplies the anterior compartment of the leg. It continues inferiorly onto the dorsal aspect of the foot. The posterior tibial artery supplies the posterior and lateral compartments of the leg and continues into the sole of the foot (Fig. 6.89). The posterior tibial artery descends through the deep region of the posterior compartment of the leg on the superficial surfaces of the tibialis posterior and flexor digitorum longus muscles. It passes through the tarsal tunnel behind the medial malleolus and into the sole of the foot. In the leg, the posterior tibial artery supplies adjacent muscles and bone and has two major branches, the circumflex fibular artery and the fibular artery:


Anatomy_Gray

Anatomy_Gray. In the leg, the posterior tibial artery supplies adjacent muscles and bone and has two major branches, the circumflex fibular artery and the fibular artery: The circumflex fibular artery passes laterally through the soleus muscle and around the neck of the fibula to connect with the anastomotic network of vessels surrounding the knee (Fig. 6.89; see also Fig. 6.80). The fibular artery parallels the course of the tibial artery, but descends along the lateral side of the posterior compartment adjacent to the medial crest on the posterior surface of the fibula, which separates the attachments of the tibialis posterior and flexor hallucis longus muscles. The fibular artery supplies adjacent muscles and bone in the posterior compartment of the leg and also has branches that pass laterally through the intermuscular septum to supply the fibularis muscles in the lateral compartment of the leg.


Anatomy_Gray

Anatomy_Gray. A perforating branch that originates from the fibular artery distally in the leg passes anteriorly through the inferior aperture in the interosseous membrane to anastomose with a branch of the anterior tibial artery. The fibular artery passes behind the attachment between the distal ends of the tibia and fibula and terminates in a network of vessels over the lateral surface of the calcaneus. Deep veins in the posterior compartment generally follow the arteries. The nerve associated with the posterior compartment of the leg is the tibial nerve (Fig. 6.90), a major branch of the sciatic nerve that descends into the posterior compartment from the popliteal fossa. The tibial nerve passes under the tendinous arch formed between the fibular and tibial heads of the soleus muscle and passes vertically through the deep region of the posterior compartment of the leg on the surface of the tibialis posterior muscle with the posterior tibial vessels.


Anatomy_Gray

Anatomy_Gray. The tibial nerve leaves the posterior compartment of the leg at the ankle by passing through the tarsal tunnel behind the medial malleolus. It enters the foot to supply most intrinsic muscles and skin. In the leg, the tibial nerve gives rise to: branches that supply all the muscles in the posterior compartment of the leg, and two cutaneous branches, the sural nerve and medial calcaneal nerve. Branches of the tibial nerve that innervate the superficial group of muscles of the posterior compartment and popliteus muscle of the deep group originate high in the leg between the two heads of the gastrocnemius muscle in the distal region of the popliteal fossa (Fig. 6.91). Branches innervate the gastrocnemius, plantaris, and soleus muscles, and pass more deeply into the popliteus muscle.


Anatomy_Gray

Anatomy_Gray. Branches to the deep muscles of the posterior compartment originate from the tibial nerve deep to the soleus muscle in the upper half of the leg and innervate the tibialis posterior, flexor hallucis longus, and flexor digitorum longus muscles. The sural nerve originates high in the leg between the two heads of the gastrocnemius muscle (Fig. 6.90). It descends superficial to the belly of the gastrocnemius muscle and penetrates through the deep fascia approximately in the middle of the leg where it is joined by a sural communicating branch from the common fibular nerve. It passes down the leg, around the lateral malleolus, and into the foot. The sural nerve supplies skin on the lower posterolateral surface of the leg and the lateral side of the foot and little toe. The medial calcaneal nerve is often multiple and originates from the tibial nerve low in the leg near the ankle and descends onto the medial side of the heel.


Anatomy_Gray

Anatomy_Gray. The medial calcaneal nerve is often multiple and originates from the tibial nerve low in the leg near the ankle and descends onto the medial side of the heel. The medial calcaneal nerve innervates skin on the medial surface and sole of the heel (Fig. 6.90). Lateral compartment of leg There are two muscles in the lateral compartment of the leg—the fibularis longus and fibularis brevis (Fig. 6.91 and Table 6.8). Both evert the foot (turn the sole outward) and are innervated by the superficial fibular nerve, which is a branch of the common fibular nerve. The fibularis longus muscle arises in the lateral compartment of the leg, but its tendon crosses under the foot to attach to bones on the medial side (Fig. 6.91). It originates from both the upper lateral surface of the fibula and from the anterior aspect of the fibular head and occasionally up onto the adjacent region of the lateral tibial condyle.


Anatomy_Gray

Anatomy_Gray. The common fibular nerve passes anteriorly around the fibular neck between the attachments of the fibularis longus to the fibular head and shaft. Distally, the fibularis longus descends in the leg to form a tendon, which, in order: passes posterior to the lateral malleolus in a shallow bony groove, swings forward to enter the lateral side of the foot, descends obliquely down the lateral side of the foot where it curves forward under a bony tubercle (fibular trochlea) of the calcaneus, enters a deep groove on the inferior surface of one of the other tarsal bones (the cuboid), and swings under the foot to cross the sole and attach to the inferior surfaces of bones on the medial side of the foot (lateral sides of the base of metatarsal I and the distal end of the medial cuneiform). The fibularis longus everts and plantarflexes the foot.


Anatomy_Gray

Anatomy_Gray. The fibularis longus everts and plantarflexes the foot. In addition, the fibularis longus, tibialis anterior, and tibialis posterior muscles, which all insert on the undersurfaces of bones on the medial side of the foot, together act as a stirrup to support the arches of the foot. The fibularis longus supports mainly the lateral and transverse arches. The fibularis longus is innervated by the superficial fibular nerve. The fibularis brevis muscle is deep to the fibularis longus muscle in the leg and originates from the lower two-thirds of the lateral surface of the shaft of the fibula (Fig. 6.91). The tendon of the fibularis brevis passes behind the lateral malleolus with the tendon of the fibularis longus muscle and then curves forward across the lateral surface of the calcaneus to attach to a tubercle on the lateral surface of the base of metatarsal V (the metatarsal associated with the little toe).


Anatomy_Gray

Anatomy_Gray. The fibularis brevis assists in eversion of the foot and is innervated by the superficial fibular nerve. No major artery passes vertically through the lateral compartment of the leg. It is supplied by branches (mainly from the fibular artery in the posterior compartment of the leg) that penetrate into the lateral compartment (Fig. 6.92). Deep veins generally follow the arteries. The nerve associated with the lateral compartment of the leg is the superficial fibular nerve. This nerve originates as one of the two major branches of the common fibular nerve, which enters the lateral compartment of the leg from the popliteal fossa (Fig. 6.92B).


Anatomy_Gray

Anatomy_Gray. The common fibular nerve originates from the sciatic nerve in the posterior compartment of the thigh or in the popliteal fossa (Fig. 6.92A), and follows the medial margin of the biceps femoris tendon over the lateral head of the gastrocnemius muscle and toward the fibula. Here it gives origin to two cutaneous branches, which descend in the leg: the sural communicating nerve, which joins the sural branch of the tibial nerve and contributes to innervation of skin over the lower posterolateral side of the leg; and the lateral sural cutaneous nerve, which innervates skin over the upper lateral leg. The common fibular nerve continues around the neck of the fibula and enters the lateral compartment by passing between the attachments of the fibularis longus muscle to the head and shaft of the fibula. Here the common fibular nerve divides into its two terminal branches: the superficial fibular nerve, and the deep fibular nerve.


Anatomy_Gray

Anatomy_Gray. The superficial fibular nerve descends in the lateral compartment deep to the fibularis longus and innervates the fibularis longus and fibularis brevis (Fig. 6.91B). It then penetrates deep fascia in the lower leg and enters the foot where it divides into medial and lateral branches, which supply dorsal areas of the foot and toes except for: the web space between the great and second toes, which is supplied by the deep fibular nerve; and the lateral side of the little toe, which is supplied by the sural branch of the tibial nerve. The deep fibular nerve passes anteromedially through the intermuscular septum into the anterior compartment of the leg, which it supplies. Anterior compartment of leg


Anatomy_Gray

Anatomy_Gray. The deep fibular nerve passes anteromedially through the intermuscular septum into the anterior compartment of the leg, which it supplies. Anterior compartment of leg There are four muscles in the anterior compartment of the leg—the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and fibularis tertius (Fig. 6.93 and Table 6.9). Collectively they dorsiflex the foot at the ankle joint, extend the toes, and invert the foot. All are innervated by the deep fibular nerve, which is a branch of the common fibular nerve. The tibialis anterior muscle is the most anterior and medial of the muscles in the anterior compartment of the leg (Fig. 6.93). It originates mainly from the upper two-thirds of the lateral surface of the shaft of the tibia and adjacent surface of the interosseous membrane. It also originates from deep fascia.


Anatomy_Gray

Anatomy_Gray. The muscle fibers of the tibialis anterior converge in the lower one-third of the leg to form a tendon, which descends into the medial side of the foot, where it attaches to the medial and inferior surfaces of one of the tarsal bones (medial cuneiform) and adjacent parts of metatarsal I associated with the great toe. The tibialis anterior dorsiflexes the foot at the ankle joint and inverts the foot at the intertarsal joints. During walking, it provides dynamic support for the medial arch of the foot. The tibialis anterior is innervated by the deep fibular nerve. The extensor hallucis longus muscle lies next to and is partly overlapped by the tibialis anterior muscle (Fig. 6.93). It originates from the middle one-half of the medial surface of the fibula and adjacent interosseous membrane.


Anatomy_Gray

Anatomy_Gray. The tendon of the extensor hallucis longus appears between the tendons of the tibialis anterior and extensor digitorum longus in the lower one-half of the leg and descends into the foot. It continues anteriorly on the medial side of the dorsal surface of the foot to near the end of the great toe where it inserts on the upper surface of the base of the distal phalanx. The extensor hallucis longus extends the great toe. Because it crosses anterior to the ankle joint, it also dorsiflexes the foot at the ankle joint. Like all muscles in the anterior compartment of the leg, the extensor hallucis longus muscle is innervated by the deep fibular nerve.


Anatomy_Gray

Anatomy_Gray. The extensor digitorum longus muscle is the most posterior and lateral of the muscles in the anterior compartment of the leg (Fig. 6.93). It originates mainly from the upper one-half of the medial surface of the fibula lateral to and above the origin of the extensor hallucis longus muscle, and extends superiorly onto the lateral condyle of the tibia. Like the tibialis anterior muscle, it also originates from deep fascia. The extensor digitorum longus muscle descends to form a tendon, which continues into the dorsal aspect of the foot, where it divides into four tendons, which insert, via dorsal digital expansions, into the dorsal surfaces of the bases of the middle and distal phalanges of the lateral four toes. The extensor digitorum longus extends the toes and dorsiflexes the foot at the ankle joint, and is innervated by the deep fibular nerve.


Anatomy_Gray

Anatomy_Gray. The extensor digitorum longus extends the toes and dorsiflexes the foot at the ankle joint, and is innervated by the deep fibular nerve. The fibularis tertius muscle is normally considered part of the extensor digitorum longus (Fig. 6.93). The fibularis tertius originates from the medial surface of the fibula immediately below the origin of the extensor digitorum longus muscle and the two muscles are normally connected. The tendon of the fibularis tertius descends into the foot with the tendon of the extensor digitorum longus. On the dorsal aspect of the foot, it deviates laterally to insert into the dorsomedial surface of the base of metatarsal V (the metatarsal associated with the little toe). The fibularis tertius assists in dorsiflexion and possibly eversion of the foot, and is innervated by the deep fibular nerve.


Anatomy_Gray

Anatomy_Gray. The fibularis tertius assists in dorsiflexion and possibly eversion of the foot, and is innervated by the deep fibular nerve. The artery associated with the anterior compartment of the leg is the anterior tibial artery, which originates from the popliteal artery in the posterior compartment of the leg and passes forward into the anterior compartment of the leg through an aperture in the interosseous membrane. The anterior tibial artery descends through the anterior compartment on the interosseous membrane (Fig. 6.94). In the distal leg, it lies between the tendons of the tibialis anterior and extensor hallucis longus muscles. It leaves the leg by passing anterior to the distal end of the tibia and ankle joint and continues onto the dorsal aspect of the foot as the dorsalis pedis artery. In the proximal leg, the anterior tibial artery has a recurrent branch, which connects with the anastomotic network of vessels around the knee joint.


Anatomy_Gray

Anatomy_Gray. In the proximal leg, the anterior tibial artery has a recurrent branch, which connects with the anastomotic network of vessels around the knee joint. Along its course, the anterior tibial artery supplies numerous branches to adjacent muscles and is joined by the perforating branch of the fibular artery, which passes forward through the lower aspect of the interosseous membrane from the posterior compartment of the leg. Distally, the anterior tibial artery gives rise to an anterior medial malleolar artery and an anterior lateral malleolar artery, which pass posteriorly around the distal ends of the tibia and fibula, respectively, and connect with vessels from the posterior tibial and fibular arteries to form an anastomotic network around the ankle. Deep veins follow the arteries and have similar names.


Anatomy_Gray

Anatomy_Gray. Deep veins follow the arteries and have similar names. The nerve associated with the anterior compartment of the leg is the deep fibular nerve (Fig. 6.94). This nerve originates in the lateral compartment of the leg as one of the two divisions of the common fibular nerve. The deep fibular nerve passes anteromedially through the intermuscular septum that separates the lateral from the anterior compartments of the leg and then passes deep to the extensor digitorum longus. It reaches the anterior interosseous membrane where it meets and descends with the anterior tibial artery. The deep fibular nerve: innervates all muscles in the anterior compartment; then continues into the dorsal aspect of the foot where it innervates the extensor digitorum brevis, contributes to the innervation of the first two dorsal interossei muscles, and supplies the skin between the great and second toes.


Anatomy_Gray

Anatomy_Gray. The foot is the region of the lower limb distal to the ankle joint. It is subdivided into the ankle, the metatarsus, and the digits. There are five digits consisting of the medially placed digits, ending laterally with the little toe (digit V) (Fig. 6.95). The foot has a superior surface (dorsum of foot) and an inferior surface (sole; Fig. 6.95). Abduction and adduction of the toes are defined with respect to the long axis of the second digit. Unlike in the hand, where the thumb is oriented 90° to the other fingers, the great toe is oriented in the same position as the other toes. The foot is the body’s point of contact with the ground and provides a stable platform for upright stance. It also levers the body forward during walking.


Anatomy_Gray

Anatomy_Gray. There are three groups of bones in the foot (Fig. 6.96): the seven tarsal bones, which form the skeletal framework for the ankle; metatarsals (I to V), which are the bones of the metatarsus; and the phalanges, which are the bones of the toes—each toe has three phalanges, except for the great toe, which has two. The tarsal bones are arranged in a proximal group and a distal group with an intermediate bone between the two groups on the medial side of the foot (Fig. 6.96A). The proximal group consists of two large bones, the talus (Latin for “ankle”) and the calcaneus (Latin for “heel”): The talus is the most superior bone of the foot and sits on top of and is supported by the calcaneus (Fig. 6.96B)—it articulates above with the tibia and fibula to form the ankle joint and also projects forward to articulate with the intermediate tarsal bone (navicular) on the medial side of the foot.


Anatomy_Gray

Anatomy_Gray. The calcaneus is the largest of the tarsal bones—posteriorly it forms the bony framework of the heel and anteriorly it projects forward to articulate with one of the distal group of tarsal bones (cuboid) on the lateral side of the foot. The talus, when viewed from the medial or lateral sides, is snail-shaped (Fig. 6.97A,B). It has a rounded head, which is projected forward and medially at the end of a short broad neck, which is connected posteriorly to an expanded body. Anteriorly, the head of the talus is domed for articulation with a corresponding circular depression on the posterior surface of the navicular bone. Inferiorly, this domed articular surface is continuous with an additional three articular facets separated by smooth ridges: The anterior and middle facets articulate with adjacent surfaces on the calcaneus bone.


Anatomy_Gray

Anatomy_Gray. The anterior and middle facets articulate with adjacent surfaces on the calcaneus bone. The other facet, medial to the facets for articulation with the calcaneus, articulates with a ligament—the plantar calcaneonavicular ligament (spring ligament)—which connects the calcaneus to the navicular under the head of the talus. The neck of the talus is marked by a deep groove (the sulcus tali), which passes obliquely forward across the inferior surface from medial to lateral, and expands dramatically on the lateral side. Posterior to the sulcus tali is a large facet (posterior calcaneal surface) for articulation with the calcaneus. The superior aspect of the body of the talus is elevated to fit into the socket formed by the distal ends of the tibia and fibula to form the ankle joint: The upper (trochlear) surface of this elevated region articulates with the inferior end of the tibia. The medial surface articulates with the medial malleolus of the tibia.


Anatomy_Gray

Anatomy_Gray. The upper (trochlear) surface of this elevated region articulates with the inferior end of the tibia. The medial surface articulates with the medial malleolus of the tibia. The lateral surface articulates with the lateral malleolus of the fibula. Because the lateral malleolus is larger and projects more inferiorly than the medial malleolus at the ankle joint, the corresponding lateral articular surface on the talus is larger and projects more inferiorly than the medial surface. The lower part of the lateral surface of the body of the talus, which supports the lower part of the facet for articulation with the fibula, forms a bony projection (the lateral process). The inferior surface of the body of the talus has a large oval concave facet (the posterior calcaneal articular facet) for articulation with the calcaneus.


Anatomy_Gray

Anatomy_Gray. The inferior surface of the body of the talus has a large oval concave facet (the posterior calcaneal articular facet) for articulation with the calcaneus. The posterior aspect of the body of the talus consists of a backward and medially facing projection (the posterior process). The posterior process is marked on its surface by a lateral tubercle and a medial tubercle, which bracket between them the groove for the tendon of the flexor hallucis longus as it passes from the leg into the foot. The calcaneus sits under and supports the talus. It is an elongate, irregular, box-shaped bone with its long axis generally oriented along the midline of the foot, but deviating lateral to the midline anteriorly (Fig. 6.98). The calcaneus projects behind the ankle joint to form the skeletal framework of the heel. The posterior surface of this heel region is circular and divided into upper, middle, and lower parts. The calcaneal tendon (Achilles tendon) attaches to the middle part:


Anatomy_Gray

Anatomy_Gray. The upper part is separated from the calcaneal tendon by a bursa. The lower part curves forward, is covered by subcutaneous tissue, is the weight-bearing region of the heel, and is continuous onto the plantar surface of the bone as the calcaneal tuberosity. The calcaneal tuberosity projects forward on the plantar surface as a large medial process and a small lateral process separated from each other by a V-shaped notch (Fig. 6.98B). At the anterior end of the plantar surface is a tubercle (the calcaneal tubercle) for the posterior attachment of the short plantar ligament of the sole of the foot.


Anatomy_Gray

Anatomy_Gray. The lateral surface of the calcaneus has a smooth contour except for two slightly raised regions (Fig. 6.98C). One of these raised areas—the fibular trochlea (peroneal tubercle)—is anterior to the middle of the surface and often has two shallow grooves, which pass, one above the other, obliquely across its surface. The tendons of the fibularis brevis and longus muscles are bound to the trochlea as they pass over the lateral side of the calcaneus. Superior and posterior to the fibular trochlea is a second raised area or tubercle for attachment of the calcaneofibular part of the lateral collateral ligament of the ankle joint. The medial surface of the calcaneus is concave and has one prominent feature associated with its upper margin (the sustentaculum tali; Fig. 6.98A), which is a shelf of bone projecting medially and supporting the more posterior part of the head of the talus.


Anatomy_Gray

Anatomy_Gray. The underside of the sustentaculum tali has a distinct groove running from posterior to anterior and along which the tendon of the flexor hallucis longus muscle travels into the sole of the foot. The superior surface of the sustentaculum tali has a facet (middle talar articular surface) for articulation with the corresponding middle facet on the head of the talus. Anterior and posterior talar articular surfaces are on the superior surface of the calcaneus itself (Fig. 6.98A): The anterior talar articular surface is small and articulates with the corresponding anterior facet on the head of the talus. The posterior talar articular surface is large and is approximately near the middle of the superior surface of the calcaneus. Between the posterior talar articular surface, which articulates with the body of the talus, and the other two articular surfaces, which articulate with the head of the talus, is a deep groove (the calcaneal sulcus; Fig. 6.98A,C).


Anatomy_Gray

Anatomy_Gray. The calcaneal sulcus on the superior surface of the calcaneus and the sulcus tali on the inferior surface of the talus together form the tarsal sinus, which is a large gap between the anterior ends of the calcaneus and talus that is visible when the skeleton of the foot is viewed from its lateral aspect (Fig. 6.99). The intermediate tarsal bone on the medial side of the foot is the navicular (boat shaped) (Fig. 6.96). This bone articulates behind with the talus and articulates in front and on the lateral side with the distal group of tarsal bones. One distinctive feature of the navicular is a prominent rounded tuberosity for the attachment of the tibialis posterior tendon, which projects inferiorly on the medial side of the plantar surface of the bone. From lateral to medial, the distal group of tarsal bones consists of (Fig. 6.96):


Anatomy_Gray

Anatomy_Gray. From lateral to medial, the distal group of tarsal bones consists of (Fig. 6.96): The cuboid (Greek for “cube”), which articulates posteriorly with the calcaneus, medially with the lateral cuneiform, and anteriorly with the bases of the lateral two metatarsals—the tendon of the fibularis longus muscle lies in a prominent groove on the anterior plantar surface, which passes obliquely forward across the bone from lateral to medial. Three cuneiforms (Latin for “wedge”)—the lateral, intermediate, and medial cuneiform bones, in addition to articulating with each other, articulate posteriorly with the navicular bone and anteriorly with the bases of the medial three metatarsals. There are five metatarsals in the foot, numbered I to V from medial to lateral (Fig. 6.100). Metatarsal I, associated with the great toe, is shortest and thickest. The second is the longest. Each metatarsal has a head at the distal end, an elongate shaft in the middle, and a proximal base.


Anatomy_Gray

Anatomy_Gray. Each metatarsal has a head at the distal end, an elongate shaft in the middle, and a proximal base. The head of each metatarsal articulates with the proximal phalanx of a toe and the base articulates with one or more of the distal group of tarsal bones. The plantar surface of the head of metatarsal I also articulates with two sesamoid bones. The sides of the bases of metatarsals II to V also articulate with each other. The lateral side of the base of metatarsal V has a prominent tuberosity, which projects posteriorly and is the attachment site for the tendon of the fibularis brevis muscle. The phalanges are the bones of the toes (Fig. 6.100). Each toe has three phalanges (proximal, middle, and distal), except for the great toe, which has only two (proximal and distal). Each phalanx consists of a base, a shaft, and a distal head: The base of each proximal phalanx articulates with the head of the related metatarsal.


Anatomy_Gray

Anatomy_Gray. Each phalanx consists of a base, a shaft, and a distal head: The base of each proximal phalanx articulates with the head of the related metatarsal. The head of each distal phalanx is nonarticular and flattened into a crescent-shaped plantar tuberosity under the plantar pad at the end of the digit. In each toe, the total length of the phalanges combined is much shorter than the length of the associated metatarsal. The ankle joint is synovial in type and involves the talus of the foot and the tibia and fibula of the leg (Fig. 6.102). The ankle joint mainly allows hinge-like dorsiflexion and plantarflexion of the foot on the leg. The distal end of the fibula is firmly anchored to the larger distal end of the tibia by strong ligaments. Together, the fibula and tibia create a deep bracket-shaped socket for the upper expanded part of the body of the talus: The roof of the socket is formed by the inferior surface of the distal end of the tibia.


Anatomy_Gray

Anatomy_Gray. The roof of the socket is formed by the inferior surface of the distal end of the tibia. The medial side of the socket is formed by the medial malleolus of the tibia. The longer lateral side of the socket is formed by the lateral malleolus of the fibula. The articular surfaces are covered by hyaline cartilage. The articular part of the talus is shaped like a short half-cylinder tipped onto its flat side with one end facing lateral and the other end facing medial. The curved upper surface of the half-cylinder and the two ends are covered by hyaline cartilage and fit into the bracket-shaped socket formed by the distal ends of the tibia and fibula.


Anatomy_Gray

Anatomy_Gray. When viewed from above, the articular surface of the talus is much wider anteriorly than it is posteriorly. As a result, the bone fits tighter into its socket when the foot is dorsiflexed and the wider surface of the talus moves into the ankle joint than when the foot is plantarflexed and the narrower part of the talus is in the joint. The joint is therefore most stable when the foot is dorsiflexed. The articular cavity is enclosed by a synovial membrane, which attaches around the margins of the articular surfaces, and by a fibrous membrane, which covers the synovial membrane and is also attached to the adjacent bones. The ankle joint is stabilized by medial (deltoid) and lateral ligaments. The medial (deltoid) ligament is large, strong (Fig. 6.103), and triangular in shape. Its apex is attached above to the medial malleolus and its broad base is attached below to a line that extends from the tuberosity of the navicular bone in front to the medial tubercle of the talus behind.


Anatomy_Gray

Anatomy_Gray. The medial ligament is subdivided into four parts based on the inferior points of attachment: The part that attaches in front to the tuberosity of the navicular and the associated margin of the plantar calcaneonavicular ligament (spring ligament), which connects the navicular bone to the sustentaculum tali of the calcaneus bone behind, is the tibionavicular part of the medial ligament. The tibiocalcaneal part, which is more central, attaches to the sustentaculum tali of the calcaneus bone. The posterior tibiotalar part attaches to the medial side and medial tubercle of the talus. The fourth part (the anterior tibiotalar part) is deep to the tibionavicular and tibiocalcaneal parts of the medial ligament and attaches to the medial surface of the talus. The lateral ligament of the ankle is composed of three separate ligaments, the anterior talofibular ligament, the posterior talofibular ligament, and the calcaneofibular ligament (Fig. 6.104):


Anatomy_Gray

Anatomy_Gray. The lateral ligament of the ankle is composed of three separate ligaments, the anterior talofibular ligament, the posterior talofibular ligament, and the calcaneofibular ligament (Fig. 6.104): The anterior talofibular ligament is a short ligament, and attaches the anterior margin of the lateral malleolus to the adjacent region of the talus. The posterior talofibular ligament runs horizontally backward and medially from the malleolar fossa on the medial side of the lateral malleolus to the posterior process of the talus. The calcaneofibular ligament is attached above to the malleolar fossa on the posteromedial side of the lateral malleolus and passes posteroinferiorly to attach below to a tubercle on the lateral surface of the calcaneus. The numerous synovial joints between the individual tarsal bones mainly invert, evert, supinate, and pronate the foot: Inversion and eversion is turning the whole sole of the foot inward and outward, respectively.


Anatomy_Gray

Anatomy_Gray. Inversion and eversion is turning the whole sole of the foot inward and outward, respectively. Pronation is rotating the front of the foot laterally relative to the back of the foot, and supination is the reverse movement. Pronation and supination allow the foot to maintain normal contact with the ground when in different stances or when standing on irregular surfaces. The major joints at which movements occur include the subtalar, talocalcaneonavicular, and calcaneocuboid joints (Fig. 6.105). The talocalcaneonavicular and calcaneocuboid joints together form what is often referred to as the transverse tarsal joint. Intertarsal joints between the cuneiforms and between the cuneiforms and the navicular allow only limited movement. The joint between the cuboid and navicular is normally fibrous.


Anatomy_Gray

Anatomy_Gray. Intertarsal joints between the cuneiforms and between the cuneiforms and the navicular allow only limited movement. The joint between the cuboid and navicular is normally fibrous. The subtalar joint is between: the large posterior calcaneal facet on the inferior surface of the talus, and the corresponding posterior talar facet on the superior surface of the calcaneus. The articular cavity is enclosed by synovial membrane, which is covered by a fibrous membrane. The subtalar joint allows gliding and rotation, which are involved in inversion and eversion of the foot. Lateral, medial, posterior, and interosseous talocalcaneal ligaments stabilize the joint. The interosseous talocalcaneal ligament lies in the tarsal sinus (Fig. 6.106). The talocalcaneonavicular joint is a complex joint in which the head of the talus articulates with the calcaneus and plantar calcaneonavicular ligament (spring ligament) below and the navicular in front (Fig. 6.107A).


Anatomy_Gray

Anatomy_Gray. The talocalcaneonavicular joint allows gliding and rotation movements, which together with similar movements of the subtalar joint are involved with inversion and eversion of the foot. It also participates in pronation and supination. The parts of the talocalcaneonavicular joint between the talus and calcaneus are: the anterior and middle calcaneal facets on the inferior surface of the talar head, and the corresponding anterior and middle talar facets on the superior surface and sustentaculum tali, respectively, of the calcaneus (Fig. 6.107B). The part of the joint between the talus and the plantar calcaneonavicular ligament (spring ligament) is between the ligament and the medial facet on the inferior surface of the talar head. The joint between the navicular and talus is the largest part of the talocalcaneonavicular joint and is between the ovoid anterior end of the talar head and the corresponding concave posterior surface of the navicular.


Anatomy_Gray

Anatomy_Gray. The capsule of the talocalcaneonavicular joint, which is a synovial joint, is reinforced: posteriorly by the interosseous talocalcaneal ligament, superiorly by the talonavicular ligament, which passes between the neck of the talus and adjacent regions of the navicular, and inferiorly by the plantar calcaneonavicular ligament (spring ligament) (Fig. 6.107C,D). The lateral part of the talocalcaneonavicular joint is reinforced by the calcaneonavicular part of the bifurcate ligament, which is a Y-shaped ligament superior to the joint. The base of the bifurcate ligament is attached to the anterior aspect of the superior surface of the calcaneus and its arms are attached to: the dorsomedial surface of the cuboid (calcaneocuboid ligament), and the dorsolateral part of the navicular (calcaneonavicular ligament).


Anatomy_Gray

Anatomy_Gray. The plantar calcaneonavicular ligament (spring ligament) is a broad thick ligament that spans the space between the sustentaculum tali behind and the navicular bone in front (Fig. 6.107B,C). It supports the head of the talus, takes part in the talocalcaneonavicular joint, and resists depression of the medial arch of the foot. The calcaneocuboid joint is a synovial joint between: the facet on the anterior surface of the calcaneus, and the corresponding facet on the posterior surface of the cuboid. The calcaneocuboid joint allows sliding and rotating movements involved with inversion and eversion of the foot, and also contributes to pronation and supination of the forefoot on the hindfoot. The calcaneocuboid joint is reinforced by the bifurcate ligament (see above) and by the long plantar ligament and the plantar calcaneocuboid ligament (short plantar ligament).


Anatomy_Gray

Anatomy_Gray. The calcaneocuboid joint is reinforced by the bifurcate ligament (see above) and by the long plantar ligament and the plantar calcaneocuboid ligament (short plantar ligament). The plantar calcaneocuboid ligament (short plantar ligament) is short, wide, and very strong, and connects the calcaneal tubercle to the inferior surface of the cuboid (Fig. 6.108A). It not only supports the calcaneocuboid joint, but also assists the long plantar ligament in resisting depression of the lateral arch of the foot. The long plantar ligament is the longest ligament in the sole of the foot and lies inferior to the plantar calcaneocuboid ligament (Fig. 6.108B): Posteriorly, it attaches to the inferior surface of the calcaneus between the tuberosity and the calcaneal tubercle. Anteriorly, it attaches to a broad ridge and a tubercle on the inferior surface of the cuboid bone behind the groove for the fibularis longus tendon.


Anatomy_Gray

Anatomy_Gray. Anteriorly, it attaches to a broad ridge and a tubercle on the inferior surface of the cuboid bone behind the groove for the fibularis longus tendon. More superficial fibers of the long plantar ligament extend to the bases of the metatarsal bones. The long plantar ligament supports the calcaneocuboid joint and is the strongest ligament, resisting depression of the lateral arch of the foot. The tarsometatarsal joints between the metatarsal bones and adjacent tarsal bones are plane joints and allow limited sliding movements (Fig. 6.109). The range of movement of the tarsometatarsal joint between the metatarsal of the great toe and the medial cuneiform is greater than that of the other tarsometatarsal joints and allows flexion, extension, and rotation. The tarsometatarsal joints, with the transverse tarsal joint, take part in pronation and supination of the foot.


Anatomy_Gray

Anatomy_Gray. The metatarsophalangeal joints are ellipsoid synovial joints between the sphere-shaped heads of the metatarsals and the corresponding bases of the proximal phalanges of the digits. The metatarsophalangeal joints allow extension and flexion, and limited abduction, adduction, rotation, and circumduction. The joint capsules are reinforced by medial and lateral collateral ligaments, and by plantar ligaments, which have grooves on their plantar surfaces for the long tendons of the digits (Fig. 6.109). Four deep transverse metatarsal ligaments link the heads of the metatarsals together and enable the metatarsals to act as a single unified structure (Fig. 6.109). The ligaments blend with the plantar ligaments of the adjacent metatarsophalangeal joints.


Anatomy_Gray

Anatomy_Gray. The metatarsal of the great toe is oriented in the same plane as the metatarsals of the other toes and is linked to the metatarsal of the second toe by a deep transverse metatarsal ligament. In addition, the joint between the metatarsal of the great toe and medial cuneiform has a limited range of motion. The great toe therefore has a very restricted independent function—unlike the thumb in the hand, where the metacarpal is oriented 90° to the metacarpals of the fingers, there is no deep transverse metacarpal ligament between the metacarpals of the thumb and index finger, and the joint between the metacarpal and carpal bone allows a wide range of motion. The interphalangeal joints are hinge joints that allow mainly flexion and extension. They are reinforced by medial and lateral collateral ligaments and by plantar ligaments (Fig. 6.109). Tarsal tunnel, retinacula, and arrangement of major structures at the ankle


Anatomy_Gray

Anatomy_Gray. Tarsal tunnel, retinacula, and arrangement of major structures at the ankle The tarsal tunnel is formed on the posteromedial side of the ankle by: a depression formed by the medial malleolus of the tibia, the medial and posterior surfaces of the talus, the medial surface of the calcaneus, and the inferior surface of the sustentaculum tali of the calcaneus; and an overlying flexor retinaculum (Fig. 6.110). The flexor retinaculum is a strap-like layer of connective tissue that spans the bony depression formed by the medial malleolus, the medial and posterior surfaces of the talus, the medial surface of the calcaneus, and the inferior surface of the sustentaculum tali (Fig. 6.110). It attaches above to the medial malleolus and below and behind to the inferomedial margin of the calcaneus. The retinaculum is continuous above with the deep fascia of the leg and below with the deep fascia (plantar aponeurosis) of the foot.


Anatomy_Gray

Anatomy_Gray. The retinaculum is continuous above with the deep fascia of the leg and below with the deep fascia (plantar aponeurosis) of the foot. Septa from the flexor retinaculum convert grooves on the bones into tubular connective tissue channels for the tendons of the flexor muscles as they pass into the sole of the foot from the posterior compartment of the leg (Fig. 6.110). Free movement of the tendons in the channels is facilitated by synovial sheaths, which surround the tendons. Two compartments on the posterior surface of the medial malleolus are for the tendons of the tibialis posterior and flexor digitorum longus muscles. The tendon of the tibialis posterior is medial to the tendon of the flexor digitorum longus.


Anatomy_Gray

Anatomy_Gray. Immediately lateral to the tendons of the tibialis posterior and flexor digitorum longus, the posterior tibial artery with its associated veins and the tibial nerve pass through the tarsal tunnel into the sole of the foot. The pulse of the posterior tibial artery can be felt through the flexor retinaculum midway between the medial malleolus and the calcaneus. Lateral to the tibial nerve is the compartment on the posterior surface of the talus and the undersurface of the sustentaculum tali for the tendon of the flexor hallucis longus muscle. Two extensor retinacula strap the tendons of the extensor muscles to the ankle region and prevent tendon bowing during extension of the foot and toes (Fig. 6.111): A superior extensor retinaculum is a thickening of deep fascia in the distal leg just superior to the ankle joint and attached to the anterior borders of the fibula and tibia.


Anatomy_Gray

Anatomy_Gray. A superior extensor retinaculum is a thickening of deep fascia in the distal leg just superior to the ankle joint and attached to the anterior borders of the fibula and tibia. An inferior retinaculum is Y-shaped, attached by its base to the lateral side of the upper surface of the calcaneus, and crosses medially over the foot to attach by one of its arms to the medial malleolus, whereas the other arm wraps medially around the foot and attaches to the medial side of the plantar aponeurosis. The tendons of the extensor digitorum longus and fibularis tertius pass through a compartment on the lateral side of the proximal foot. Medial to these tendons, the dorsalis pedis artery (terminal branch of the anterior tibial artery), the tendon of the extensor hallucis longus muscle, and finally the tendon of the tibialis anterior muscle pass under the extensor retinacula.


Anatomy_Gray

Anatomy_Gray. Fibular (peroneal) retinacula bind the tendons of the fibularis longus and fibularis brevis muscles to the lateral side of the foot (Fig. 6.112): A superior fibular retinaculum extends between the lateral malleolus and the calcaneus. An inferior fibular retinaculum attaches to the lateral surface of the calcaneus around the fibular trochlea and blends above with the fibers of the inferior extensor retinaculum. At the fibular trochlea, a septum separates the compartment for the tendon of the fibularis brevis muscle above from that for the fibularis longus below. Arches of the foot The bones of the foot do not lie in a horizontal plane. Instead, they form longitudinal and transverse arches relative to the ground (Fig. 6.113), which absorb and distribute downward forces from the body during standing and moving on different surfaces.


Anatomy_Gray

Anatomy_Gray. The longitudinal arch of the foot is formed between the posterior end of the calcaneus and the heads of the metatarsals (Fig. 6.113A). It is highest on the medial side, where it forms the medial part of the longitudinal arch, and lowest on the lateral side, where it forms the lateral part. The transverse arch of the foot is highest in a coronal plane that cuts through the head of the talus and disappears near the heads of the metatarsals, where these bones are held together by the deep transverse metatarsal ligaments (Fig. 6.113B). Ligaments and muscles support the arches of the foot (Fig. 6.114): Ligaments that support the arches include the plantar calcaneonavicular (spring ligament), plantar calcaneocuboid (short plantar ligament), and long plantar ligaments, and the plantar aponeurosis. Muscles that provide dynamic support for the arches during walking include the tibialis anterior and posterior and the fibularis longus.


Anatomy_Gray

Anatomy_Gray. Muscles that provide dynamic support for the arches during walking include the tibialis anterior and posterior and the fibularis longus. The plantar aponeurosis is a thickening of deep fascia in the sole of the foot (Fig. 6.115). It is firmly anchored to the medial process of the calcaneal tuberosity and extends forward as a thick band of longitudinally arranged connective tissue fibers. The fibers diverge as they pass anteriorly and form digital bands, which enter the toes and connect with bones, ligaments, and dermis of the skin. Distal to the metatarsophalangeal joints, the digital bands of the plantar aponeurosis are interconnected by transverse fibers, which form superficial transverse metatarsal ligaments. The plantar aponeurosis supports the longitudinal arch of the foot and protects deeper structures in the sole. Fibrous sheaths of toes


Anatomy_Gray

Anatomy_Gray. The plantar aponeurosis supports the longitudinal arch of the foot and protects deeper structures in the sole. Fibrous sheaths of toes The tendons of the flexor digitorum longus, flexor digitorum brevis, and flexor hallucis longus muscles enter fibrous digital sheaths or tunnels on the plantar aspect of the digits (Fig. 6.116). These fibrous sheaths begin anterior to the metatarsophalangeal joints and extend to the distal phalanges. They are formed by fibrous arches and cruciate (cross-shaped) ligaments attached posteriorly to the margins of the phalanges and to the plantar ligaments associated with the metatarsophalangeal and interphalangeal joints. These fibrous tunnels hold the tendons to the bony plane and prevent tendon bowing when the toes are flexed. Within each tunnel, the tendons are surrounded by a synovial sheath.


Anatomy_Gray

Anatomy_Gray. These fibrous tunnels hold the tendons to the bony plane and prevent tendon bowing when the toes are flexed. Within each tunnel, the tendons are surrounded by a synovial sheath. The tendons of the extensor digitorum longus, extensor digitorum brevis, and extensor hallucis longus pass into the dorsal aspect of the digits and expand over the proximal phalanges to form complex dorsal digital expansions (“extensor hoods”) (Fig. 6.117). Each extensor hood is triangular in shape with the apex attached to the distal phalanx, the central region attached to the middle (toes II to V) or proximal (toe I) phalanx, and each corner of the base wrapped around the sides of the metatarsophalangeal joint. The corners of the hoods attach mainly to the deep transverse metatarsal ligaments.


Anatomy_Gray

Anatomy_Gray. Many of the intrinsic muscles of the foot insert into the free margin of the hood on each side. The attachment of these muscles into the extensor hoods allows the forces from these muscles to be distributed over the toes to cause flexion of the metatarsophalangeal joints while at the same time extending the interphalangeal joints (Fig. 6.117). The function of these movements in the foot is uncertain, but they may prevent overextension of the metatarsophalangeal joints and flexion of the interphalangeal joints when the heel is elevated off the ground and the toes grip the ground during walking.


Anatomy_Gray

Anatomy_Gray. Intrinsic muscles of the foot originate and insert in the foot: the extensor digitorum brevis and extensor hallucis brevis on the dorsal aspect of the foot; all other intrinsic muscles—the dorsal and plantar interossei, flexor digiti minimi brevis, flexor hallucis brevis, flexor digitorum brevis, quadratus plantae (flexor accessorius), abductor digiti minimi, abductor hallucis, and lumbricals—are on the plantar side of the foot in the sole where they are organized into four layers. Intrinsic muscles mainly modify the actions of the long tendons and generate fine movements of the toes. All intrinsic muscles of the foot are innervated by the medial and lateral plantar branches of the tibial nerve except for the extensor digitorum brevis, which is innervated by the deep fibular nerve. The first two dorsal interossei also may receive part of their innervation from the deep fibular nerve. On the dorsal aspect


Anatomy_Gray

Anatomy_Gray. On the dorsal aspect The extensor digitorum brevis is attached to a roughened area on the superolateral surface of the calcaneus lateral to the tarsal sinus (Fig. 6.118 and Table 6.10). The flat muscle belly passes anteromedially over the foot, deep to the tendons of the extensor digitorum longus, and forms three tendons, which enter digits II, III, and IV. The tendons join the lateral sides of the tendons of the extensor digitorum longus. The extensor digitorum brevis extends the middle three toes through attachments to the long extensor tendons and extensor hoods. It is innervated by the deep fibular nerve. The extensor hallucis brevis originates in conjunction with the extensor digitorum brevis. Its tendon attaches to the base of the proximal phalanx of the great toes. The muscle extends the metatarsophalangeal joint of the great toe and is innervated by the deep fibular nerve. In the sole


Anatomy_Gray

Anatomy_Gray. In the sole The muscles in the sole of the foot are organized into four layers. From superficial to deep, or plantar to dorsal, these layers are the first, second, third, and fourth layers. There are three components in the first layer of muscles, which is the most superficial of the four layers and is immediately deep to the plantar aponeurosis (Fig. 6.119 and Table 6.11). From medial to lateral, these muscles are the abductor hallucis, flexor digitorum brevis, and abductor digiti minimi. The abductor hallucis muscle forms the medial margin of the foot and contributes to a soft tissue bulge on the medial side of the sole (Fig. 6.119). It originates from the medial process of the calcaneal tuberosity and adjacent margins of the flexor retinaculum and plantar aponeurosis. It forms a tendon that inserts on the medial side of the base of the proximal phalanx of the great toe and on the medial sesamoid bone associated with the tendon of the flexor hallucis brevis muscle.


Anatomy_Gray

Anatomy_Gray. The abductor hallucis abducts and flexes the great toe at the metatarsophalangeal joint and is innervated by the medial plantar branch of the tibial nerve. The flexor digitorum brevis muscle lies immediately superior to the plantar aponeurosis and inferior to the tendons of the flexor digitorum longus in the sole of the foot (Fig. 6.119). The flat spindle-shaped muscle belly originates as a tendon from the medial process of the calcaneal tuberosity and from the adjacent plantar aponeurosis. The muscle fibers of the flexor digitorum brevis converge anteriorly to form four tendons, which each enter one of the lateral four toes. Near the base of the proximal phalanx of the toe, each tendon splits to pass dorsally around each side of the tendon of the flexor digitorum longus and attach to the margins of the middle phalanx. The flexor digitorum brevis flexes the lateral four toes at the proximal interphalangeal joints and is innervated by the medial plantar branch of the tibial nerve.


Anatomy_Gray

Anatomy_Gray. The flexor digitorum brevis flexes the lateral four toes at the proximal interphalangeal joints and is innervated by the medial plantar branch of the tibial nerve. The abductor digiti minimi muscle is on the lateral side of the foot and contributes to the large lateral plantar eminence on the sole (Fig. 6.119). It has a broad base of origin, mainly from the lateral and medial processes of the calcaneal tuberosity and from a fibrous band of connective tissue, which connects the calcaneus with the base of metatarsal V. The abductor digiti minimi forms a tendon, which travels in a shallow groove on the plantar surface of the base of metatarsal V and continues forward to attach to the lateral side of the base of the proximal phalanx of the little toe. The abductor digiti minimi abducts the little toe at the metatarsophalangeal joint and is innervated by the lateral plantar branch of the tibial nerve.


Anatomy_Gray

Anatomy_Gray. The abductor digiti minimi abducts the little toe at the metatarsophalangeal joint and is innervated by the lateral plantar branch of the tibial nerve. The second muscle layer in the sole of the foot is associated with the tendons of the flexor digitorum longus muscle, which pass through this layer, and consists of the quadratus plantae and four lumbrical muscles (Fig. 6.120 and Table 6.12). The quadratus plantae muscle is a flat quadrangular muscle with two heads of origin (Fig. 6.120): One of the heads originates from the medial surface of the calcaneus inferior to the sustentaculum tali. The other head originates from the inferior surface of the calcaneus anterior to the lateral process of the calcaneal tuberosity and the attachment of the long plantar ligament. The quadratus plantae muscle inserts into the lateral side of the tendon of the flexor digitorum longus in the proximal half of the sole of the foot near where the tendon divides.


Anatomy_Gray

Anatomy_Gray. The quadratus plantae muscle inserts into the lateral side of the tendon of the flexor digitorum longus in the proximal half of the sole of the foot near where the tendon divides. The quadratus plantae assists the flexor digitorum longus tendon in flexing the toes and may also adjust the “line of pull” of this tendon as it enters the sole of the foot from the medial side. The muscle is innervated by the lateral plantar nerve. The lumbrical muscles are four worm-like muscles that originate from the tendons of the flexor digitorum longus and pass dorsally to insert into the free medial margins of the extensor hoods of the four lateral toes (Fig. 6.120). The first lumbrical originates from the medial side of the tendon of the flexor digitorum longus that is associated with the second toe. The remaining three muscles are bipennate and originate from the sides of adjacent tendons.


Anatomy_Gray

Anatomy_Gray. The lumbrical muscles act through the extensor hoods to resist excessive extension of the metatarsophalangeal joints and flexion of the interphalangeal joints when the heel leaves the ground during walking. The first lumbrical is innervated by the medial plantar nerve, while the other three are innervated by the lateral plantar nerve. There are three muscles in the third layer in the sole of the foot (Fig. 6.122 and Table 6.13): Two (the flexor hallucis brevis and adductor hallucis) are associated with the great toe. The third (the flexor digiti minimi brevis) is associated with the little toe. The flexor hallucis brevis muscle has two tendinous heads of origin (Fig. 6.122): The lateral head originates from the plantar surfaces of the cuboid, behind the groove for the fibularis longus, and adjacent surface of the lateral cuneiform. The medial head originates from the tendon of the tibialis posterior muscle as it passes into the sole of the foot.


Anatomy_Gray

Anatomy_Gray. The medial head originates from the tendon of the tibialis posterior muscle as it passes into the sole of the foot. The medial and lateral heads unite and give rise to a muscle belly, which itself is separated into medial and lateral parts adjacent to the plantar surface of metatarsal I. Each part of the muscle gives rise to a tendon that inserts on either the lateral or medial side of the base of the proximal phalanx of the great toe. A sesamoid bone occurs in each tendon of the flexor hallucis brevis as it crosses the plantar surface of the head of metatarsal I. The tendon of the flexor hallucis longus passes between the sesamoid bones. The flexor hallucis brevis flexes the metatarsophalangeal joint of the great toe and is innervated by the medial plantar nerve. The adductor hallucis muscle originates by two muscular heads, transverse and oblique, which join near their ends to insert into the lateral side of the base of the proximal phalanx of the great toe (Fig. 6.122):


Anatomy_Gray

Anatomy_Gray. The transverse head originates from the plantar ligaments associated with the metatarsophalangeal joints of the lateral three toes and from the associated deep transverse metatarsal ligaments—the muscle crosses the sole of the foot transversely from lateral to medial and joins the oblique head near the base of the great toe. The oblique head is larger than the transverse head and originates from the plantar surfaces of the bases of metatarsals II to IV and from the sheath covering the fibularis longus muscle—this head passes anterolaterally through the sole of the foot and joins the transverse head. The tendon of insertion of the adductor hallucis attaches to the lateral sesamoid bone associated with the tendon of the flexor hallucis brevis muscle in addition to attaching to the proximal phalanx. The adductor hallucis adducts the great toe at the metatarsophalangeal joint and is innervated by the lateral plantar nerve.


Anatomy_Gray

Anatomy_Gray. The adductor hallucis adducts the great toe at the metatarsophalangeal joint and is innervated by the lateral plantar nerve. The flexor digiti minimi brevis muscle originates from the plantar surface of the base of metatarsal V and adjacent sheath of the fibularis longus tendon (Fig. 6.122). It inserts on the lateral side of the base of the proximal phalanx of the little toe. The flexor digiti minimi brevis flexes the little toe at the metatarsophalangeal joint and is innervated by the lateral plantar nerve. There are two muscle groups in the deepest muscle layer in the sole of the foot, the dorsal and plantar interossei (Fig. 6.123 and Table 6.14). The four dorsal interossei are the most superior muscles in the sole of the foot and abduct the second to fourth toes relative to the long axis through the second toe (Fig. 6.123). All four muscles are bipennate and originate from the sides of adjacent metatarsals.


Anatomy_Gray

Anatomy_Gray. The tendons of the dorsal interossei insert into the free margin of the extensor hoods and base of the proximal phalanges of the toes. The second toe can be abducted to either side of its long axis, so it has two dorsal interossei associated with it, one on each side. The third and fourth toes have a dorsal interosseous muscle on their lateral sides only. The great and little toes have their own abductors (the abductor hallucis and abductor digiti minimi) in the first layer of muscles in the sole of the foot. In addition to abduction, the dorsal interossei act through the extensor hoods to resist extension of the metatarsophalangeal joints and flexion of the interphalangeal joints. The dorsal interossei are innervated by the lateral plantar nerve. The first and second dorsal interossei also receive branches on their superior surfaces from the deep fibular nerve.


Anatomy_Gray

Anatomy_Gray. The dorsal interossei are innervated by the lateral plantar nerve. The first and second dorsal interossei also receive branches on their superior surfaces from the deep fibular nerve. The three plantar interossei adduct the third, fourth, and little toes toward the long axis through the second toe (Fig. 6.123). Each plantar interosseous muscle originates from the medial side of its associated metatarsal and inserts into the medial free margin of the extensor hood and base of the proximal phalanx. The great toe has its own adductor (the adductor hallucis) in the third layer of muscles in the sole of the foot and the second toe is adducted back to its longitudinal axis by using one of its dorsal interossei. In addition to adduction, the plantar interossei act through the extensor hoods to resist extension of the metatarsophalangeal joints and flexion of the interphalangeal joints. All are innervated by the lateral plantar nerve.


Anatomy_Gray

Anatomy_Gray. Blood supply to the foot is by branches of the posterior tibial and dorsalis pedis (dorsal artery of the foot) arteries. The posterior tibial artery enters the sole and bifurcates into lateral and medial plantar arteries. The lateral plantar artery joins with the terminal end of the dorsalis pedis artery (the deep plantar artery) to form the deep plantar arch. Branches from this arch supply the toes. The dorsalis pedis artery is the continuation of the anterior tibial artery, passes onto the dorsal aspect of the foot and then inferiorly, as the deep plantar artery, between metatarsals I and II to enter the sole of the foot.


Anatomy_Gray

Anatomy_Gray. The posterior tibial artery enters the foot through the tarsal tunnel on the medial side of the ankle and posterior to the medial malleolus. Midway between the medial malleolus and the heel, the pulse of the posterior tibial artery is palpable because here the artery is covered only by a thin layer of retinaculum, by superficial connective tissue, and by skin. Near this location, the posterior tibial artery bifurcates into a small medial plantar artery and a much larger lateral plantar artery.


Anatomy_Gray

Anatomy_Gray. The lateral plantar artery passes anterolaterally into the sole of the foot, first deep to the proximal end of the abductor hallucis muscle and then between the quadratus plantae and flexor digitorum brevis muscles (Fig. 6.124). It reaches the base of metatarsal V where it lies in the groove between the flexor digitorum brevis and abductor digiti minimi muscles. From here, the lateral plantar artery curves medially to form the deep plantar arch, which crosses the deep plane of the sole on the metatarsal bases and the interossei muscles. Between the bases of metatarsals I and II, the deep plantar arch joins with the terminal branch (deep plantar artery) of the dorsalis pedis artery, which enters the sole from the dorsal side of the foot.


Anatomy_Gray

Anatomy_Gray. Major branches of the deep plantar arch include: a digital branch to the lateral side of the little toe; four plantar metatarsal arteries, which supply digital branches to adjacent sides of toes I to V and the medial side of the great toe; and three perforating arteries, which pass between the bases of metatarsals II to V to anastomose with vessels on the dorsal aspect of the foot. The medial plantar artery passes into the sole of the foot by passing deep to the proximal end of the abductor hallucis muscle (Fig. 6.124). It supplies a deep branch to adjacent muscles and then passes forward in the groove between the abductor hallucis and the flexor digitorum brevis muscles. It ends by joining the digital branch of the deep plantar arch, which supplies the medial side of the great toe.


Anatomy_Gray

Anatomy_Gray. Near the base of metatarsal I, the medial plantar artery gives rise to a superficial branch, which divides into three vessels that pass superficial to the flexor digitorum brevis muscle to join the plantar metatarsal arteries from the deep plantar arch. The dorsalis pedis artery is the continuation of the anterior tibial artery and begins as the anterior tibial artery crosses the ankle joint (Fig. 6.125). It passes anteriorly over the dorsal aspect of the talus, navicular, and intermediate cuneiform bones, and then passes inferiorly, as the deep plantar artery, between the two heads of the first dorsal interosseous muscle to join the deep plantar arch in the sole of the foot. The pulse of the dorsalis pedis artery on the dorsal surface of the foot can be felt by gently palpating the vessel against the underlying tarsal bones between the tendons of the extensor hallucis longus and the extensor digitorum longus to the second toe.


Anatomy_Gray

Anatomy_Gray. Branches of the dorsalis pedis artery include lateral and medial tarsal branches, an arcuate artery, and a first dorsal metatarsal artery: The tarsal arteries pass medially and laterally over the tarsal bones, supplying adjacent structures and anastomosing with a network of vessels formed around the ankle. The arcuate artery passes laterally over the dorsal aspect of the metatarsals near their bases and gives rise to three dorsal metatarsal arteries, which supply dorsal digital arteries to adjacent sides of digits II to V, and to a dorsal digital artery that supplies the lateral side of digit V. The first dorsal metatarsal artery (the last branch of the dorsalis pedis artery before the dorsalis pedis artery continues as the deep plantar artery into the sole of the foot) supplies dorsal digital branches to adjacent sides of the great and second toes.


Anatomy_Gray

Anatomy_Gray. The dorsal metatarsal arteries connect with perforating branches from the deep plantar arch and similar branches from the plantar metatarsal arteries. There are interconnected networks of deep and superficial veins in the foot. The deep veins follow the arteries. Superficial veins drain into a dorsal venous arch on the dorsal surface of the foot over the metatarsals (Fig. 6.126): The great saphenous vein originates from the medial side of the arch and passes anterior to the medial malleolus and onto the medial side of the leg. The small saphenous vein originates from the lateral side of the arch and passes posterior to the lateral malleolus and onto the back of the leg. The foot is supplied by the tibial, deep fibular, superficial fibular, sural, and saphenous nerves: All five nerves contribute to cutaneous or general sensory innervation.


Anatomy_Gray

Anatomy_Gray. The foot is supplied by the tibial, deep fibular, superficial fibular, sural, and saphenous nerves: All five nerves contribute to cutaneous or general sensory innervation. The tibial nerve innervates all intrinsic muscles of the foot except for the extensor digitorum brevis, which is innervated by the deep fibular nerve. The deep fibular nerve often also contributes to the innervation of the first and second dorsal interossei. The tibial nerve enters the foot through the tarsal tunnel posterior to the medial malleolus. In the tunnel, the nerve is lateral to the posterior tibial artery, and gives origin to medial calcaneal branches, which penetrate the flexor retinaculum to supply the heel. Midway between the medial malleolus and the heel, the tibial nerve bifurcates with the posterior tibial artery into: a large medial plantar nerve, and a smaller lateral plantar nerve (Fig. 6.127). The medial and lateral plantar nerves lie together between their corresponding arteries.


Anatomy_Gray

Anatomy_Gray. The medial and lateral plantar nerves lie together between their corresponding arteries. The medial plantar nerve is the major sensory nerve in the sole of the foot (Fig. 6.127). It innervates skin on most of the anterior two-thirds of the sole and adjacent surfaces of the medial three and one-half toes, which includes the great toe. In addition to this large area of plantar skin, the nerve also innervates four intrinsic muscles—the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and first lumbrical. The medial plantar nerve passes into the sole of the foot deep to the abductor hallucis muscle and forward in the groove between the abductor hallucis and flexor digitorum brevis, supplying branches to both these muscles.


Anatomy_Gray

Anatomy_Gray. The medial plantar nerve supplies a digital branch (proper plantar digital nerve) to the medial side of the great toe and then divides into three nerves (common plantar digital nerves) on the plantar surface of the flexor digitorum brevis, which continue forward to supply proper plantar digital branches to adjacent surfaces of toes I to IV. The nerve to the first lumbrical originates from the first common plantar digital nerve. The lateral plantar nerve is an important motor nerve in the foot because it innervates all intrinsic muscles in the sole, except for the muscles supplied by the medial plantar nerve (the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and first lumbrical) (Fig. 6.127). It also innervates a strip of skin on the lateral side of the anterior two-thirds of the sole and the adjacent plantar surfaces of the lateral one and one-half digits.


Anatomy_Gray

Anatomy_Gray. The lateral plantar nerve enters the sole of the foot by passing deep to the proximal attachment of the abductor hallucis muscle. It continues laterally and anteriorly across the sole between the flexor digitorum brevis and quadratus plantae muscles, supplying branches to both these muscles, and then divides near the head of metatarsal V into deep and superficial branches. The superficial branch of the lateral plantar nerve gives rise to a proper plantar digital nerve, which supplies skin on the lateral side of the little toe, and to a common plantar digital nerve, which divides to supply proper plantar digital nerves to skin on the adjacent sides of toes IV and V. The proper plantar digital nerve to the lateral side of the little toe also innervates the flexor digiti minimi brevis and the dorsal and plantar interossei muscles between metatarsals IV and V.


Anatomy_Gray

Anatomy_Gray. The proper plantar digital nerve to the lateral side of the little toe also innervates the flexor digiti minimi brevis and the dorsal and plantar interossei muscles between metatarsals IV and V. The deep branch of the lateral plantar nerve is motor and accompanies the lateral plantar artery deep to the long flexor tendons and the adductor hallucis muscle. It supplies branches to the second to fourth lumbrical muscles, the adductor hallucis muscle, and all interossei except those between metatarsals IV and V, which are innervated by the superficial branch. The deep fibular nerve innervates the extensor digitorum brevis, contributes to the innervation of the first two dorsal interossei muscles, and supplies general sensory branches to the skin on the adjacent dorsal sides of the first and second toes and to the web space between them (Fig. 6.128).


Anatomy_Gray

Anatomy_Gray. The deep fibular nerve enters the dorsal aspect of the foot on the lateral side of the dorsalis pedis artery, and is parallel with and lateral to the tendon of the extensor hallucis longus muscle. Just distal to the ankle joint, the nerve gives origin to a lateral branch, which innervates the extensor digitorum brevis from its deep surface. The deep fibular nerve continues forward on the dorsal surface of the foot, penetrates deep fascia between metatarsals I and II near the metatarsophalangeal joints, and then divides into two dorsal digital nerves, which supply skin over adjacent surfaces of toes I and II down to the beginning of the nail beds. Small motor branches, which contribute to the supply of the first two dorsal interossei muscles, originate from the deep fibular nerve before it penetrates deep fascia.


Anatomy_Gray

Anatomy_Gray. Small motor branches, which contribute to the supply of the first two dorsal interossei muscles, originate from the deep fibular nerve before it penetrates deep fascia. The superficial fibular nerve is sensory to most skin on the dorsal aspect of the foot and toes except for skin on adjacent sides of toes I and II (which is innervated by the deep fibular nerve) and skin on the lateral side of the foot and little toe (which is innervated by the sural nerve; Fig. 6.128). The superficial fibular nerve penetrates deep fascia on the anterolateral side of the lower leg and enters the dorsal aspect of the foot in superficial fascia. It gives rise to cutaneous branches and dorsal digital nerves along its course.


Anatomy_Gray

Anatomy_Gray. The sural nerve is a cutaneous branch of the tibial nerve that originates high in the leg. It enters the foot in superficial fascia posterior to the lateral malleolus close to the short saphenous vein. Terminal branches innervate skin on the lateral side of the foot and dorsolateral surface of the little toe (Fig. 6.128B). The saphenous nerve is a cutaneous branch of the femoral nerve that originates in the thigh. Terminal branches enter the foot in superficial fascia on the medial side of the ankle and supply skin on the medial side of the proximal foot (Fig. 6.128B). Tendons, muscles, and bony landmarks in the lower limb are used to locate major arteries, veins, and nerves.


Anatomy_Gray

Anatomy_Gray. Tendons, muscles, and bony landmarks in the lower limb are used to locate major arteries, veins, and nerves. Because vessels are large, they can be used as entry points to the vascular system. In addition, vessels in the lower limb are farthest from the heart and the most inferior in the body. Therefore, the nature of peripheral pulses in the lower limb can give important information about the status of the circulatory system in general. Sensation and muscle action in the lower limb are tested to assess lumbar and sacral regions of the spinal cord. Avoiding the sciatic nerve


Anatomy_Gray

Anatomy_Gray. Sensation and muscle action in the lower limb are tested to assess lumbar and sacral regions of the spinal cord. Avoiding the sciatic nerve The sciatic nerve innervates muscles in the posterior compartment of the thigh, muscles in the leg and foot, and an appreciable area of skin. It enters the lower limb in the gluteal region (Fig. 6.129) and passes inferiorly midway between two major palpable bony landmarks, the greater trochanter and the ischial tuberosity. The greater trochanter can be easily felt as a hard bony protuberance about one hand’s width inferior to the midpoint of the iliac crest. The ischial tuberosity is palpable just above the gluteal fold. The gluteal region can be divided into quadrants by two lines positioned using palpable bony landmarks. One line descends vertically from the highest point of the iliac crest.


Anatomy_Gray

Anatomy_Gray. The gluteal region can be divided into quadrants by two lines positioned using palpable bony landmarks. One line descends vertically from the highest point of the iliac crest. The other line passes horizontally through the first line midway between the highest point of the iliac crest and the horizontal plane through the ischial tuberosity. The sciatic nerve curves through the upper lateral corner of the lower medial quadrant and descends along the lateral margin of the lower medial quadrant. Injections can be carried out in the anterior corner of the upper lateral quadrant to avoid injury to the sciatic nerve and major vessels in the region (Fig. 6.129B). Finding the femoral artery in the femoral triangle The femoral artery passes into the femoral triangle (Fig. 6.130) of the lower limb from the abdomen.


Anatomy_Gray

Anatomy_Gray. Finding the femoral artery in the femoral triangle The femoral artery passes into the femoral triangle (Fig. 6.130) of the lower limb from the abdomen. The femoral triangle is the depression formed in the anterior thigh between the medial margin of the adductor longus muscle, the medial margin of the sartorius muscle, and the inguinal ligament. The tendon of the adductor longus muscle can be palpated as a cord-like structure that attaches to bone immediately inferior to the pubic tubercle. The sartorius muscle originates from the anterior superior iliac spine and crosses anteriorly over the thigh to attach to the medial aspect of the tibia below the knee joint. The inguinal ligament attaches to the anterior superior iliac spine laterally and the pubic tubercle medially.


Anatomy_Gray

Anatomy_Gray. The inguinal ligament attaches to the anterior superior iliac spine laterally and the pubic tubercle medially. The femoral artery descends into the thigh from the abdomen by passing under the inguinal ligament and into the femoral triangle. In the femoral triangle, its pulse is easily felt just inferior to the inguinal ligament midway between the pubic symphysis and the anterior superior iliac spine. Medial to the artery is the femoral vein and medial to the vein is the femoral canal, which contains lymphatics and lies immediately lateral to the pubic tubercle. The femoral nerve lies lateral to the femoral artery. Identifying structures around the knee


Anatomy_Gray

Anatomy_Gray. Identifying structures around the knee The patella is a prominent palpable feature at the knee. The quadriceps femoris tendon attaches superiorly to it and the patellar ligament connects the inferior surface of the patella to the tibial tuberosity (Fig. 6.131). The patellar ligament and the tibial tuberosity are easily palpable. A tap on the patellar ligament (tendon) tests reflex activity mainly at spinal cord levels L3 and L4. The head of the fibula is palpable as a protuberance on the lateral surface of the knee just inferior to the lateral condyle of the tibia. It can also be located by following the tendon of the biceps femoris inferiorly. The common fibular nerve passes around the lateral surface of the neck of the fibula just inferior to the head and can often be felt as a cord-like structure in this position.


Anatomy_Gray

Anatomy_Gray. The common fibular nerve passes around the lateral surface of the neck of the fibula just inferior to the head and can often be felt as a cord-like structure in this position. Another structure that can usually be located on the lateral side of the knee is the iliotibial tract. This flat tendinous structure, which attaches to the lateral tibial condyle, is most prominent when the knee is fully extended. In this position, the anterior edge of the tract raises a sharp vertical fold of skin posterior to the lateral edge of the patella. Visualizing the contents of the popliteal fossa


Anatomy_Gray

Anatomy_Gray. Visualizing the contents of the popliteal fossa The popliteal fossa is a diamond-shaped depression formed between the hamstrings and gastrocnemius muscle posterior to the knee. The inferior margins of the diamond are formed by the medial and lateral heads of the gastrocnemius muscle. The superior margins are formed laterally by the biceps femoris muscle and medially by the semimembranosus and semitendinosus muscles. The tendons of the biceps femoris muscle and the semitendinosus muscle are palpable and often visible. The head of the fibula is palpable on the lateral side of the knee and can be used as a landmark for identifying the biceps femoris tendon and the common fibular nerve, which curves laterally out of the popliteal fossa and crosses the neck of the fibula just inferior to the head.


Anatomy_Gray

Anatomy_Gray. The popliteal fossa contains the popliteal artery, the popliteal vein, the tibial nerve, and the common fibular nerve (Fig. 6.132). The popliteal artery is the deepest of the structures in the fossa and descends through the region from the upper medial side. As a consequence of its position, the popliteal artery pulse is difficult to find, but usually can be detected on deep palpation just medial to the midline of the fossa. The small saphenous vein penetrates deep fascia in the upper part of the posterior leg and joins the popliteal vein. Finding the tarsal tunnel—the gateway to the foot The tarsal tunnel (Fig. 6.133) is formed on the medial side of the foot in the groove between the medial malleolus and the heel (calcaneal tuberosity) and by the overlying flexor retinaculum.