Vincent Chassaing MD

Anterior Cruciate Ligament

The anterior cruciate ligament is located deep inside the center of the knee. Roughly speaking, it forms an X with the posterior cruciate ligament which crosses just behind it. Together they limit the front to back motion of the lower leg relative to the upper leg. Specifically, the anterior cruciate ligament (ACL) limits the forward displacement of the lower leg. It also limits the internal rotation of the tibia relative to the femur. When the knee is suddenly twisted, especially when the foot is planted, it is common for the ACL to be torn. These are classic ski and football injuries as the foot is commonly locked in place as the body twists around it. The tear of the ligament is not uncommonly associated with an audible crack. The diagnosis is then made by a combination of the physical examination and imaging studies such as MRIs. The ACL does not heal. Nevertheless, a tear of the ACL does not preclude normal function of the knee during everyday activities. However, when the knee is subject to considerable twisting, as in a number of athletic activities, a torn ACL can lead to an unstable knee. In this setting, one can consider surgical reconstruction of this ligament (for example, by harvesting a tendon from the same knee). The decision of whether to operate or not depends a great deal on the age of the patient and the demands that the patient wishes to place on his or her knee (i.e. the type of sport the patient wishes to play).