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What is a Medial Collateral Ligament (MCL) Injury?

There are 4 main ligaments that support the knee joint. The two cruciate (cross) ligaments, the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL), are on the inside of the knee joint and connect the tibia to the femur. The two collateral ligaments of the knee, the medial collateral ligament (MCL) and the lateral collateral ligament (LCL), are on the outside of the knee. The MCL connects the femur to the tibia, and the LCL connects the femur to the fibula (smaller bone of the lower leg).

MCL injuries are some of the most common ligamentous injuries sustained in an athletic population. Usually MCL injuries occur when a force pushing the knee inwards (medially) occurs. This can occur from direct contact, such as a helmet to the outside of the knee, or can occur during a pivoting or cutting, alongside other ligamentous injuries (such as ACL injuries). The valgus (inward force) places stress on the MCL, causing tearing. There are can be partial or complete sprains/ tears of the MCL; severity of the sprain or tear dictates the treatment course.


  • Secondary to blunt force to the outside of the knee forcing the knee inwards (valgus)
  • Awkward landings from a jump; knee valgus (knee collapsing inwards)

Signs & Symptoms

  • Swelling over the injured ligament (inside of the knee)
  • Often painful over inside (medial) aspect of knee
  • Oftentimes athletes will note hearing or feeling a “pop”
  • Feelings of instability or ‘giving way’


Management of MCL injuries is rarely surgical because unlike the anterior cruciate ligament (ACL), the MCL has a good blood supply and will eventually heal on its own if treated properly. Initial treatment for MCL injuries is to reduce the acute inflammation in the knee. Rest from sports and activities, ice, elevation and compression are essential in the early stages following injury. Use of crutches is oftentimes used following injury due to pain with weight bearing. Bracing of the knee is commonly utilized to help allow adequate healing of the ligament. The knee brace will protect the knee from giving out or “collapsing” inwards during activities of daily living.

Once the initial pain and inflammation are decreased, weaning off of the crutches and regaining normal range of motion and strength through physical therapy and home exercises is important in order to maintain knee function. The length of recovery is dependent on the severity of the sprain or tear. Injuries to the MCL are normally classified in three grades. Grade 1 sprains are classified as a ligament that has been slightly stretched, but is still able support the joint. Grade 2 sprains are where the ligament is stretched to the point of becoming loose and is partially torn. The most severe of the sprains is a grade 3 sprain and is commonly referred to as a complete tear of the ligament, causing the knee joint to be unstable. Again, most isolated MCL tears do not require surgery and will heal on its own. However, if there is other ligamentous damage in the knee, the success of conservative treatment may decrease; decision on surgical intervention to repair the damaged collateral ligament is made on a case-by-case basis by the orthopedic surgeon.

Following an adequate period of rest and rehabilitative therapy, along with decreased pain and instability, the athlete may begin a slow progression back into activity as tolerated. Continued bracing of the knee during activity is not uncommon for those athletes wishing to provide added stability to their knee upon first returning back to sport.

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