A ligament is a tissue anywhere in the body that connects one bone to another. Within the knee, four ligaments stabilize the joint: the Posterior Cruciate Ligament, Anterior Cruciate Ligament, the Lateral Collateral Ligament and the Medial Collateral Ligament, or MCL. This report details what occurs when your MCL tears, either completely or partially. An injury to the MCL or any other ligament is known as a "sprain," or, more commonly, a "tear" when it is most severe. Should the ligament separate from its attachment to the bone, it is known as an "avulsion."

The MCL runs from the inside (medial) portion of the femur (thighbone) to the medial side of the tibia (shinbone). The durable ligament prevents the lower leg from moving laterally, or toward the outside. A sprain to the ligament, most often brought on by a blow directly to the inside of the lower leg, can happen in one of three "grades":

• Grade 1, in which the ligament is stretched, but not torn.
  
• Grade 2, where the MCL is partially torn.
  
• Grade 3, in which the MCL is completely torn and instability, or looseness of the joint, occurs.

Depending upon the degree or combination of injury, an orthopedic surgeon may decide to operate or pursue conservative methods to manage the MCL tear. The vast majority of MCL tears are treated conservatively with a hinged knee brace. Depending upon the severity of the blow, an MCL tear may be accompanied by a fractured tibia or femur.