ACL vs. MCL Tears: What is the Difference?

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A tearing of one’s anterior cruciate ligament (ACL) or medial collateral ligament (MCL) can be incredibly debilitating, regardless of whether or not the patient is an athlete. These types of knee injuries can make everyday tasks much more difficult, and the recovery time can take several months. While these skeletal injuries are commonly associated with one another, and at times concurrent, they are actually quite different.

The ACL and MCL are just two of four total ligaments within the knee with the posterior cruciate ligament (PCL) and lateral collateral ligament (LCL) being the others. While knee injuries can damage any one of these ligaments, the ACL and MCL are the most commonly affected. The ACL is located in the middle of the knee joint that connects the femur to the tibia. It limits knee rotation and forward motion of the tibia. The MCL is a longer ligament that runs the length of the back of the knee joint, limiting sideways motion of the knee.

A tear of either of these ligaments is almost instantly recognizable, as many patients feel or hear a pop (more commonly in ACL tears), followed by swelling (caused by internal bleeding in the knee) and pain. Experiencing a locked knee or not being able to straighten it is another sign of a serious knee injury (meniscus tear). Following the sensation of a pop, your knee may also become unstable, making standing and walking difficult. Weakness upon trying to straighten the knee is another clear sign of a possible ACL or MCL tear.

ACL tears are typically caused by a sudden twist or dislocation of the knee. Stopping or changing directions suddenly while running puts a great amount of stress on this ligament, as does landing awkwardly from a jump. Twisting your foot after planting it can also twist the ACL itself. Even direct hits to the knee can damage the ACL enough to cause a partial or a complete tear.

MCL tears are usually caused by a widening of the ligament after contact, most often from sports. Patients will feel pain or tenderness in the inner part of the knee, as well as weakness or occasional locking. Tears of this ligament are classified as either grade 1, 2, or 3 tears. Grade 1 MCL injuries are when the ligament is overstretched, but not torn. Grade 2 injuries are partially torn MCLs, and Grade 3 injuries are complete tears.

If you feel you’ve sustained a knee injury that could be either of these types of ligamentous tears, assess your symptoms to determine which of the two it might be. As previously mentioned, ACL tears often come with a distinct popping noise unlike MCL tears. However, the symptoms experienced are very similar in both injuries (swelling, pain, and bruising). Check with your doctor immediately upon sustaining any type of knee injury to determine which is the optimal course for you.Initial period of ice, elevation and immobilization is wise. Early MEI is frequently needed to secure a definitive diagnosis and treatment plan.

Treating the two injuries differ greatly as well. MCLs tend to heal much more easily than ACLs, as their recovery process typically lasts roughly 8-9 weeks, and requires physical rehabilitation. ACL tears on the other hand, almost always requires surgical repair, and can take up to 9 months to fully heal.

For a torn MCL, it is recommended to ice the knee, bandage it, keep it elevated, and use crutches if possible. Combined with physical rehabilitation, the ligament should heal itself. Surgery may only be required if it is unable to do so. Because of the multiple ligaments within the ACL, surgery is usually required upon tearing it.

For athletes especially, understanding how to prevent these serious knee injuries is important. Consider wearing a knee brace during sports or physical activity, exercise the necessary muscles to strengthen your knee, and always avoid overexertion. As always, proper warm up before strenuous activities and regular conditioning is paramount to safe engagement with recreational activity. Stay toned!