Anterior cruciate ligament (ACL) is one of the four main ligaments of the knee. Ligaments are bands of strong fibrous connective tissues that hold bones in position. The other three ligaments of the knee are the posterior cruciate ligament (PCL), medial collateral ligament (MCL), and the lateral collateral ligament (LCL). The ACL helps connect the tibia (the large bone of the lower leg) to the femur (thigh bone). The ACL also contains arteries and nerves. The ACL functions to stabilize the knee and prevent front-to-back motion of the joint so that the knee moves like a hinge.
Most injuries of the ACL are associated with sporting activities. Injuries include stretching and partial or full tears of the ligament. ACL injuries usually occur when an athlete twists the knee while making a sudden stop and turn, such as in basketball, football, or soccer. Athletes who injure their ACL often hear a snap or popping sound from the knee and have a feeling of the knee “giving way” and becoming unstable. Pain and swelling of the knee follows. Physicians diagnose ACL injuries through examination of the knee. X rays and magnetic resonance imaging (MRI) are often used to diagnose and confirm an ACL tear. ACL tears may be accompanied by another injury, including damage to knee cartilage and other ligaments.
Initial treatment of an ACL tear includes applying ice to reduce inflammation and a knee brace to provide support, using pain medication, and keeping the knee elevated when possible. Patients with a torn ACL may require crutches to walk. ACL tears will not heal on their own. Physicians recommend surgery to repair the ACL and allow a return to normal activities, and to prevent arthritis. Surgeons use an arthroscope while repairing a torn ACL. An arthroscope is a straight, tubelike instrument with a series of lenses and a fiber-optical light source. It can be inserted into a joint through a small incision, thereby allowing surgeons to view the joint and make repairs. Surgeons place a new ligament between the tibia and the femur. After surgery, physical therapy helps the patient regain full function of the knee. A patient can often return to normal activities, including athletics, in five to six months following surgery.
See also Knee .
