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 Medial Collateral Ligament, and the Lateral Collateral Ligament, or LCL. This report details what occurs when your LCL tears, either completely or partially. An injury to the LCL 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 LCL runs from the outside (lateral) portion of the femur (thighbone) to the lateral side of the tibia (shinbone). The durable ligament prevents the lower leg from moving medially, or toward the inside. A sprain to the ligament, most often brought on by a blow directly to 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 LCL is partially torn.
  
• Grade 3, in which the LCL is completely torn and instability, or looseness of the joint, occurs.