The medial collateral ligament (MCL) is a strong flat band of fibrous tissue that extends from the medial epicondyle of the femur (thigh bone) to the medial plateau of the tibia (shin bone). The MCL is one of four ligaments that are critical to the stability of the knee joint; the other three ligaments are the anterior and posterior cruciate ligaments (ACL and PCL, respectively), and the lateral collateral ligament (LCL)/posterolateral corner complex. The MCL functions to limit how much the outside of the knee opens during movement.
The MCL is typically injured from a blow to the outside of the knee. Once the ligament tears, it heals very slowly. An MCL tear can occur as an isolated injury or it can be associated with other knee injuries, in particular tears of the ACL and medial meniscus. The combination of an ACL tear, MCL tear, and medial meniscus tear is referred to as the “unhappy triad.”
The most common symptom following an MCL injury is pain directly over the ligament on the inside (medial side) of the knee. Knee pain, swelling, and decreased motion are common with this injury. Symptoms of a medial collateral ligament injury tend to correlate with the extent of the injury. MCL injuries are graded on a scale of I to III. A grade I injury is a small tear within the ligament. A grade II injury is a medium sized tear. A grade III injury is a complete tear of the MCL, which is usually associated with tears of other knee ligaments.
Most MCL tears heal on their own without the need for surgery. A brace is often prescribed to protect the ligament while it heals. Grade I and grade II injuries usually resolve within 4-6 weeks, though full recovery may take longer. During this time, it is important to work on strengthening the surrounding muscle groups and physical therapy is often prescribed. Grade III injuries are more severe injuries that are usually associated with tears of other ligaments in the knee and may require surgery. Surgical repair of the MCL is usually done through an open incision and involves stitching the ligament back down to the bone. Postoperative recovery is variable and depends on what other injuries are present in the knee.