ACL vs MCL Tear: Know the Differences


ACL vs MCL Tear: Know the Differences

People often ask about the difference between an ACL tear and an MCL tear. ACL and MCL are two out of four major knee ligaments that stabilize the knee. The ACL (anterior cruciate ligament) is located in the middle of your knee which can prevent the femur from sliding backward on the tibia, while MCL (Medial Collateral Ligament) is a band of tissue on the inside of your knee to connect your thigh bone and the bone of your lower leg which prevents your knee from bending inward. The MCL is a ligament that provides stability to the inner knee whereas the ACL controls forward movement and rotation of the shin bone from the center of the knee.

ACL and MCL tears are the most common knee injuries during sports or activities that involve twisting, bending and quick change of direction. For sports like skiing, basketball and soccer with many stop and go motions, jumping can be the common cause for ACL and MCL injuries. The main differences between an ACL and an MCL tear are a significant amount of swelling often occurs when you injured the ACL as well as the amount of instability when walking after the ACL injury. Generally speaking, the MCL has a much higher healing potential than the ACL. Torn ACL patients are more likely to rely on crutches or knee brace for walking after the injury. ACL and MCL tears can also be combined with multi-ligament injuries of the knee. A grade 3 MCL tear can be generally occurred along with a torn ACL.

What are the Differences between ACL and MCL Tears?

ACL vs. MCL: Location

The ACL is located in the middle of the knee to prevent shin bone from sliding out in front of the thighbone whereas the MCL is located on the inside of the knee, which is external to the knee joint. As the name suggested, MCL (medial collateral ligament) is located on the medial side of the knee. The exact location of MCL can be described as within the inner part of the knee from the bottom of the thighbone to a point on the top of shinbone, which is about 4-6 inches from the knee. The locations of ACL and MCL and where it can be torn are indicated in the following diagram:


ACL vs. MCL Tears

The ACL is responsible for stabilizing the knee while keeping the knee from turning too much and preventing the tibia from overextending itself. A torn ACL generally occurs when you are playing sports, trauma (caused from falling), changing directions quickly and stopping suddenly. Age is also a risk factor that can contribute to ACL injuries. A popping sound can often be heard when the injury has occurred. The injured ACL can be categorized as a completely torn ACL or a completely torn ACL. The ACL is usually injured by a sudden twisting motion from the knee or dislocation.

Similar to an ACL tear, an MCL tear is often caused by playing contact sports and trauma, but it’s injured when the force is applied to the medial side of the knee that is external to the knee joint. The MCL is usually injured when the outer side of the knee has been hit by strong force to cause strain on the medial side of the knee. Any activities that involved with frequent pivoting like soccer, team handball, basketball, and figure skating are presenting a higher risk to cause ACL and MCL tears. You might also experience a popping sound for MCL injuries which is similar to an ACL tear.

In general, ACL and MCL injuries occur when too much stress is put on the knee joint. Repetitive motions and excessive force overtime can be the main contributing factors to cause ACL and MCL tears. A ligament tear can be really painful and the recovery process can take long time before you can fully ready to return to sports.

An ACL and an MCL tear can be graded on a scale from one to three as grade I, II or III where grade I is a minor injury and a grade III is a complete tear. Patients with grade I injury can usually return their sport but it does not, implying that surgery is necessary for patients with grade III injury to return to sports. The definition for each grade can be slightly different but this grade is all given depending on the degree of sustained tear. Please find the comparison for grades of injury for ACL and MCL tears below:

ACL Grades of Injury MCL Grades of Injury
  • Grade I - the fibers of the ligament are stretched but no fibers are torn with a little tenderness and swelling. No unstable feeling when you are walking or participating in an activity
  • Grade II - the ligament is partially torn or incomplete tear with hemorrhage. The knee joint might feel unstable during activity
  • Grade III - the fibers of the ligament are completely torn into two parts. The level of pain will be subject to the severity of the injury with a little or a lot of swelling
  • Grade I - mild injury with minimally torn collagen fibers less than 10% and no loss of MCL integrity with some tenderness but no instability
  • Grade II - moderate injury with a partial tear and increased laxity of the MCL by having tenderness but no instability
  • Grade III - severe injury as a completely torn MCL with significant pain and swelling over the MCL with difficulty to bend the knee which can also result in instability

ACL vs MCL: Symptom Comparison

The symptoms for ACL and MCL tears are similar but a few key differences may help you to distinguish the injury is causing by a torn ACL or MCL. The typical common symptoms for an ACL and MCL tear are: limited range of motion, inflammation, swelling, knee pain and possible bruising.

The main differences of symptoms between an ACL tear and an MCL tear are:

  • The location of the knee pain and swelling. The pain and swelling will typically from the middle of your knee for an ACL tear whereas the pain and swelling are usually from the inner side of the knee joint for an MCL tear
  • ACL injuries will generally have a more distinctive popping sound than an MCL tear
  • The knee typically becomes very swollen and unstable after ACL injuries
ACL Tear Symptoms MCL Tear Symptoms
  • Sharp pain
  • Swollen knee
  • Difficulty walking, standing
  • Limited range of motion
  • The injured knee “gives out”
  • Can’t straighten or fully extend the injured leg
  • Pain when weight bearing on the knee
  • Pain from the inner side of the injured knee
  • The injured knee “gives out”
  • Swelling
  • Locked knee
  • Feeling unstable to walk

ACL vs MCL tears: Cause Comparison

ACL injuries often occurred when the tibia is pushed forward in front of the femur. A direct blow to the front of the knee is the common cause of ACL injuries. These injuries are more common during a fall when you are skiing or play basketball and football that involved a sudden change in direction, which can stress and damage the ACL.

Similar to an ACL tear, an MCL tear often occurs in contact sports that require a lot of pivoting when the knee is forced to bend, twist or pivot to the side in an unnatural way. An MCL tear is often caused by the strong force hitting hard to the outer knee, which resulted in strain on the inner knee.

Knee Ligament Injuries Common Cause of Injury
ACL Tear Sudden change of direction or sudden stop during sports. A hard landing from a jump often causes a torn ACL. The bending, twisting and changing direction rapidly are the common motions during skiing, basketball and football that can cause ACL injuries.
MCL Tear MCL tear is commonly caused by a direct blow to the outside of the knee. MCL injuries can often occur in contact sports such as football. MCL is prone to be stretched and partial or complete tearing in football or other contact sports.

ACL vs. MCL tears: Diagnosis

The diagnosis of a torn ACL can be confirmed by physical examination by comparing the injured knee and uninjured knee to check the severity of the injury. MRI (magnetic resonance imaging) is a more accurate way to exam soft tissues like ACL with better images.

Similar to the diagnosis of a torn ACL, A doctor should be able to diagnose an MCL tear after performing a physical examination of the knee to compare the injured knee with the other. A physical exam will also check for any swelling and find out the location of the tenderness. MRI or other radiographs may also be required to diagnose a severe MCL.

The benefit of using an MRI to diagnose an MCL tear is that MRI images can show the detailed representations of the tissues that make up your MCL, which can help doctors to identify the exact location of an MCL tear. Using MRI to diagnose the MCL tear is a proper and effective way to improve your chances of a smooth recovery.

Although surgery might not be necessary for ACL and MCL tears, we still highly recommend you to visit your doctor for diagnosis and treatment.

ACL vs. MCL tears: Treatment and Recovery

Treatment for an ACL tear is generally more complicated than an MCL tear. Moderate to severe (grade II to III) ACL tears often require surgery and longer recovery time. If you want to be able to fully return to sports after being diagnosed for a completely torn ACL, an ACL reconstruction surgery may be required. The recovery time for ACL injuries can take more than 6 months to 1 year, depending on the severity of the injury and what types of sports the patients are returning after the recovery.

In contrast, an MCL rarely requires surgery, people who suffered an MCL often be able to return to their favorite sports because most MCL injuries can heal on its own after approximately 8 weeks of rehabilitation.

Most of MCL tears can be treated at home with a combination of adequate rest, cold therapy, and anti-inflammatory medicine. You may reply on crutches or a hinged knee brace to support your knee after the injury, and you should reduce your level of activity during the first a few weeks.

According to Dr. Dodds, the recovery process of ACL and MCL injuries is very similar, the main difference is the recovery speed at which the patients can return to sports.

We highly recommend patients to see an orthopedic surgeon or specialist for further evaluation and treatment.

Nonsurgical Treatment Options for ACL and MCL tears

Nonsurgical treatment options are available for ACL and MCL tears when surgery is not required. Nonsurgical treatments generally consist of the following methods:

  • Adequate rest for the knee and avoid pivoting or walking during the first a few days or weeks after the injury
  • Cold therapy to reduce swelling and pain by using an ice pack
  • Wearing compression knee sleeve to improve blood circulation around the knee joint to promote recovery
  • Keep your injured leg elevated at a minimum of a 45-degree angle to reduce swelling
  • Wear a knee brace to support the injured knee and protect it from side-to-side movement during healing
  • Use crutches during the first a few days or weeks after the injuries or surgery to avoid weight-bearing on the injured leg
  • Physical therapy can also help patients to regain normal movement in the knee by starting with gentile exercises based on your physical therapist’s advice

Take away: ACL vs. MCL tears which is worse?

As discussed in the previous section, both ACL and MCL tears can be classified in three grades depending on the severity of the injury. MCL tears are usually easier to recover from than ACL tears. Generally speaking, the ACL is considered as the worst ligament in the knee to tear. An ACL tear is often worse than an MCL tear due to the following reasons:

  • An ACL tear often requires reconstruction surgery and longer rehab time
  • Patients with a surgically repaired ACL are more likely to tear the ACL in the uninjured knee
  • Recovery time for ACL injuries can easily take more than 6 months. It is much longer MCL injuries which generally require 8 weeks recovery
  • The injured knee with a torn ACL is typically very swollen results in instability in the knee
  • The MCL has a much higher healing potential than the ACL
  • The MCL has a better blood supply compared to ACL because the MCL is located outside the knee joint which is in a more conducive environment for heading because it’s not impeded by joint fluid inside the knee joint

To sum up, MCL injuries heal relatively quickly, in some cases, patients with a torn MCL could return to action in just two weeks, whereas ACL injuries can keep patients away from sports for months up to a year. However, no matter which one is worse between an ACL tear and an MCL tear. We highly recommend the injury to be assessed and treated by an orthopedic surgeon with no delays to prevent causing any further damage to the injured knee.

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