The medial collateral ligament (MCL) is a broad, thick band that runs down the inner part of the knee, from the femur (thighbone) to about four to six inches from the top of the tibia (shinbone).The MCL's primary function is to prevent the leg from over-extending inward, but it also is part of the mechanism that stabilizes the knee and allows it to rotate.
Injuries to the MCL commonly occur as a result of a strong force hitting the outside of the knee that causes the MCL — and, possibly, other ligaments on the inside of the knee, such as the anterior cruciate ligament (ACL) — to stretch or tear.
This can happen while playing sports, for example during a clip block in football, where one player collides with another player from the side. In addition, MCL tears occur in sports where there are a lot of quick stops and turns, such as soccer, basketball and skiing. Slipping on ice, if your lower leg splays out, also can produce the same result. Another cause of injury is repeated stress, where the MCL loses its normal elasticity and becomes limp, like a worn-out rubber band.
Initial symptoms of an MCL tear include:
Symptoms occur along the inner side of the knee. (The MCL is located on the side of the knee adjacent to the other knee.) Depending on the severity of the injury, pain can range from mild to severe.
In addition, the knee may feel unsteady, or may lock or "catch."
Your doctor will likely ask how you injured your knee, how it has been feeling since the injury and if you've injured your knee before. He or she will check for pain or tenderness along the inside of the knee. In addition, your doctor will approximate the cause of the injury by exerting pressure on the outside of your knee while your leg is both bent and straight.
Depending on the degree of pain or looseness of your knee joint, the injury will be classified as one of three grades:
On average, it takes six weeks for a MCL injury to heal. The initial treatment for most grade 1, 2 or 3 MCL tears focuses on reducing the pain and inflammation in the knee while immobilizing the knee to keep it stabilized. This includes:
The cast or brace may be designed so that you cannot bend your knee at all. If this is the case, you will need to modify your behavior so that you can avoid having to squat, kneel down or bend over. You should try to keep your leg elevated even if you are sitting in a chair, to reduce blood flow to the knee.
Reviewed by health care specialists at UCSF Medical Center.