Anterior cruciate ligament (ACL) injuries are one of the most common sports injuries in the United States. The ACL is one of the most important ligaments in the body, and is crucial to providing stability of the knee joint. Unfortunately, the ACL has poor healing potential, and ACL surgery is required to reconstruct the torn ligament in most cases. In some cases, however, the ACL can be repaired in a way that it will heal. Most of the time, repair is not possible and a reconstruction is needed. ACL reconstruction surgery is done by taking a tendon from somewhere else in the body (or from a donor) and using it to replace the torn ACL.