Ringbone and Sidebone

Back when the sound of heavy, steel-shod hooves rang out on cobblestone streets, every horse owner was familiar with the signs--heat, swelling, shortened or shuffling stride, and the bony ridges developing where all used to be smooth and sleek. Ringbone and sidebone, two closely related orthopedic problems of the lower limbs, used to be considered almost inevitable hallmarks of the working harness horse, and they are still distressingly common in horses which deal with heavy-duty concussive forces and those with certain conformational problems. There are no miraculous cures for either condition, but like many other arthritic states, it's possible to manage ringbone and sidebone once you understand what you're dealing with.

The Riddle of Ringbone

Ringbone, or phalangeal exostosis, is actually a catch-all phrase for one syndrome that can occur in two different locations. In ringbone, calcification (the formation of excess mineral deposits, which eventually ossify or become bony) occurs on the pastern bones, interfering with joint function and flexibility. Depending on its location and the structures involved, it can be designated "high ringbone," "low ringbone‚" or "false ringbone."

High ringbone occurs when calcification accumulates where the long pastern bone, or P1, and the short pastern bone, P2, meet. The mineral deposits, which are the body's response to chronic inflammation, form a partial or complete ring around the bones at the joint, hence the name. Outwardly, ringbone becomes easily visible as a bony ridge about halfway down one or both pasterns of the forelegs. In its early stages, it might only be spotted on radiographs.

The more calcification, and the closer it is to the joint surfaces, the more obvious ringbone becomes, and the more it causes the bones to grate on each other with every step. Eventually, however, the calcification results in the joint fusing, stabilizing the area. After that, ringbone is considered "cold" or "set," and it often creates no further lameness or heat (although the joint no longer bends).

Low ringbone is essentially the same process of calcification, except that it forms at the joint between the short pastern bone (P2) and the coffin bone (P3), causing a hard ridge in the area of the coronary band. Horses can develop either high or low ringbone, or both, over time.

Because the joint between P2 and P3 is so mobile, low ringbone is considered more serious than high ringbone; in fact, for many decades veterinarians and anatomists figured that the P1-P2 joint really didn't flex much at all. Slow-motion video reveals that it does actually play a role in normal motion, but horses whose P1-P2 joint has fused generally learn to compensate very well and travel soundly, once the heat and irritation have resolved.

Says Jeff Thomason, PhD, a specialist in equine biomechanics and anatomy at the Ontario Veterinary College at the University of Guelph, "High ringbone can be debilitating while it's hot. Once it's set, you lose a little motion between the P1 and P2, but horses seem to be able to live without it."

It's not unusual, Thomason adds, for the development of ringbone in one location to contribute to its development in the other joint, as well. "A horse with high ringbone compensates for the lost motion in the P1-P2 joint, and in doing so, he may further irritate the P2-P3 joint, triggering calcification there. It doesn't always happen, but sometimes you end up with ringbone in both joints."

The more calcification, of course, the greater the challenge to soundness; Thomason suggests that a horse diagnosed with high ringbone might be retired from high-impact work, such as jumping, to cut the risk that he'll develop low ringbone as well.

Farrier Warwick Bloomfield, who shoes near London, England, says he's had the opposite experience. "I think most horses tend to develop low ringbone first," he says. "Then high ringbone develops as a secondary response to the limited flexion in the coffin joint from the low ringbone."

Despite our increased understanding of anatomy and the arthritic process, there's still no cure for ringbone. "It's a degenerative process, so it's going to get worse over time," says veterinarian and farrier Stephen O'Grady, DVM, whose practice in The Plains, Va., focuses on equine podiatry. "The symptoms may be easy to miss at first--the horse may be reluctant to go forward or start to refuse jumps, or his gait may become short or shuffling. There may be a low-grade lameness, which can look like heel pain. Usually, it will only be visible when the horse is working, not when he's turned out in the field. The lameness will become more pronounced on hard surfaces. In my experience, one leg is usually worse than the other, but there's often some degree of calcification in both front pasterns. When one leg becomes affected, of course, the horse tends to favor it and put more pressure on the opposite leg, so eventually that one becomes inflamed, too, and the degenerative process begins."

Thomason notes that he sees more cases of bilateral (both front legs involved) ringbone in Standardbreds, which tend to put equal stress on both forelegs traveling at a trot or a pace, and unilateral (one front or hind leg only) ringbone in breeds such as Thoroughbreds.

The degree of severity of ringbone depends largely on where the calcification occurs on the pastern bones and how much accumulates. "Calcification on the top and bottom of the bones is more problematic than ridges which develop on the sides," says Thomason. "If the ridges are banging into each other every time the horse flexes the joint to take a stride, he's going to be very uncomfortable. Fortunately, calcification tends to occur where ligaments attach to the bone, so often it ends up forming around the lateral ligaments on the sides of the coffin (P2-P3) joint. The ligaments can still move when that happens, so the joint flexion isn't all that limited as a rule."

Ringbone Diagnosis

In the developmental stages, heat and swelling associated with ringbone might come and go. Rest might resolve the lameness temporarily, but because the process of calcification is likely continuing beneath the surface, the inflammation and soreness will return when the horse goes back to work. Longeing or riding in circles can make the lameness more evident and help in diagnosis. With low ringbone, you might notice a reluctance to flex the joint, including a possible resistance to having the lower limb flexed for hoof cleaning or farrier work.

In its earliest stages, ringbone can probably be best diagnosed using infrared thermography to reveal the inflammation (and increased thermal patterns) along the pastern bones. But most cases aren't identified until the calcification is formed and it shows up on radiographs. Nerve blocks can help zero in on the pastern, as the source of the pain helps differentiate ringbone from some other conditions that can cause subtle lameness, such as tendonitis, osteochondritis dissecans, chip fractures, and navicular-like heel pain.

If your horse is lucky, his radiographs might show little or no calcification in his pastern joints, leading your veterinarian to diagnose false ringbone. False ringbone produces similar clinical signs to real ringbone, but this inflammation involves the ligaments between the pastern bones and/ or the joint capsule rather than being the result of bony calcification. Unlike the real thing, it usually resolves with rest, although it can be a warning sign for future arthritic changes.

See ringbone and sidebone radiographs here.

Several factors can predispose a horse to ringbone. "Age, work, and concussive forces are the three things I think make a horse most prone to ringbone," Thomason says. "It tends to occur mostly in older horses who have worked on hard surfaces much of their lives. The repeated pounding takes its toll. The horses most at risk are probably those with long toes and low heels, which creates increased leverage on the fetlock and pastern. But horses who are too upright in their pasterns or have very high heels can be at risk, too."

Certified Journeyman Farrier Chris Zizian of Milton, Ontario, agrees that horses with short, upright pasterns and high or contracted heels can be predisposed to ringbone. "Any time you get a lot of concussive forces that aren't being absorbed by the foot, the joints are going to get inflamed," he says.

From O'Grady's perspective, both of the pastern joints are affected by movement and breakover. "The harder the horse has to work for breakover, the more force and stress on the joints," he says. "If the hoof/ pastern axis is broken back--in other words, the horse has long toes and low heels--or broken forward--which is the opposite extreme--the joints have to work very hard, and inevitably they get irritated. In a nutshell, what you have to do is normalize the hoof/pastern axes so they are parallel, then the breakover is eased and so is the irritation. You can't stop the process (of calcification), but at least you can prevent it from getting any worse!"

Shoeing Help For Ringbone

The usual approach in easing breakover for a ringbone sufferer is to apply a rolled-toe or rockered-toe shoe, square off the toe, or even consider the squared-off-behind-the-toe design of a natural balance shoe. O'Grady says. "Anything which moves the breakover back is good," he adds.

An affected horse which is idle might be able to get away with being barefoot, but the majority of horses expected to remain in some kind of work will benefit from being shod, he says. "I use radiographs as a guide for trimming and shoeing these horses. It's useful to see exactly where the ossification is occurring."

Many farriers like to give a horse with ringbone a little extra protection from concussive forces by using a wide-webbed shoe and possibly adding a pad. O'Grady, however, prefers to allow a ringbone sufferer to grow a good, thick sole callus and resist the temptation to trim the sole.

Other Treatments

In the early stages of ringbone, some veterinarians have had good success in arresting the degenerative process by temporarily limiting the mobility of the affected joint or joints with a Robert-Jones bandage or a light cast. For other horses, a few weeks of stall rest will suffice, along with aggressive cold therapy (to reduce swelling and inflammation) followed by warm, moist heat therapy (to encourage good circulation and rapid healing). While you're addressing the initial trauma, you can also take steps to modify your horse's shoeing and re-assess his training program in order to preserve as much of his soundness as possible. Remember that ringbone is a response to repeated concussion, so an eventer might find his athletic future in the dressage ring, and an urban police horse might have to find another vocation on softer footing.

Non-steroidal anti-inflammatory drugs, such as phenylbutazone (Bute), can help alleviate pain in ringbone's developmental stages, and your veterinarian might suggest injectable sodium hyaluronate or polysulfated glycosaminoglycans (PSGAGs). In some cases of high ringbone that don't self-resolve, it can be helpful to artificially fuse the pastern joint by surgical arthrodesis (usually by inserting a couple of screws through the joint to immobilize it). But this approach isn't practical with low ringbone, because the P2-P3 joint is much more mobile than P1-P2.

See severe ringbone cases here.

Sidebone: All Kidding Aside

Sidebone used to be the curse of the working draft horse, and it's still seen most often in the gentle giants of the equine world. Like ringbone, this syndrome is a degenerative, arthritic process, but in the case of sidebone, it's the lateral cartilages that extend backward like wings from the side processes of the coffin bone (P3) to the bulbs of the heel that calcify and harden. As they do, the heel bulbs lose their elasticity and become rigid on palpation. The end result is a hoof with a limited ability to expand and contract with the impact of each stride. In radiographs and on dissection, sidebone often appears as two dramatically large, hard extensions on either side of the coffin bone.

Draft horses are predisposed to sidebone because of the sheer weight of their bodies on their hoof structures. Years of work on hard, unyielding surfaces only increase the risk. Like ringbone, sidebone tends to develop in older horses; in fact, it's considered almost a normal rite of passage for the lateral cartilages to ossify to some degree over time, and the process is only designated as sidebone when it is premature or happens abnormally fast and leads to lameness.

Poor conformation and/or poor shoeing can put a horse at risk for sidebone. As in ringbone, uneven stresses on the foot--especially those that limit its ability to absorb shock--cause continued trauma to the cartilages and trigger the inflammatory process. Bloomfield says, "Inappropriate loading of the foot, and especially shoeing that results in the frog not touching the ground and thus not functioning as it should, are what contributes to the cartilages calcifying, in my opinion. From a farrier's perspective, the concussive forces are multiplied in draft horses, but any horse who is obese might be at risk as well."

The good news is that sidebone doesn't usually result in major lameness. Most often, affected horses will find palpation of the area just above their heel bulbs painful, but won't show any change in gait. "The horse may be tender, but not dramatically lame," says Thomason. "(Sidebone) isn't something that develops overnight. It's a chronic problem and results in limited give in the heel area, but for a draft horse who's likely not doing much galloping, it's something he can live with."

O'Grady agrees, saying, "In heavy horses, the lateral cartilages come larger from the factory, and the weight of the horse predisposes them to ossifying. But often the horse doesn't even know (the problem) is there. I have to say I've never seen a diagnosed sidebone that caused lameness on its own. If the horse is lame, there's usually something else going on as well.

"In terms of shoeing, I usually ignore sidebone--it's something that doesn't look particularly good on a radiograph, but it's not a major issue as far as I'm concerned."

Zizian notes, "I don't see a lot of sidebone because I mostly shoe sport horses. But I may run across the odd draft-cross who has a touch of it. Reducing concussion, with rolled or square toes, and maybe raising the heels, are the traditional treatments. If the horse is really sore, I may try something I've had success with once or twice--applying clips in the heel area to minimize heel expansion when the leg is bearing weight. It's contrary to absolutely everything we've been taught, but I've seen it relieve the discomfort on a couple of occasions when nothing else has worked."

In most cases, however, the emphasis should be placed on correctly balancing the foot to discourage any further calcification, and on reducing concussion by working only on yielding surfaces and possibly applying shock-absorbing pads. As with ringbone, you should put your focus on managing the condition rather than curing it.

Fortunately, neither ringbone nor sidebone is likely to end your horse's career. Instead, take these conditions as warning signs. Arthritic changes such as these are a way of alerting you that it might be time to throttle back on the athletic demands you place on your horse and find a kinder, gentler road for him to travel as he ages. There's nothing wrong with that--it's something many of us could do as well.

About the Author

Karen Briggs



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