The ACL (Anterior Cruciate Ligament) is one of the four main ligaments in the knee (figure 1). The ACL provides rotational stability and support to help prevent unnatural movement in the joint. High impact activities that feature rapid, twisting movements place extreme forces on the knees, which can lead to injury. Basketball, football, and skiing are common activities that can tear or damage an ACL, resulting in a loss of stability in the knee. ACL reconstruction is the most common form of treatment for patients who require the use of a stable knee for athletic sports, walking, or other low-impact activities.