Sports Medicine: Anterior Cruciate Ligament (ACL) Injury
What is an anterior cruciate ligament (ACL) injury?
The anterior cruciate ligament (ACL) is a ligament in the knee that joins the front part of the tibia (shin bone) to the back part of the femur (thigh bone). The ACL provides support to prevent the shin bone from sliding forward while walking and running. It is located behind the patella.
What causes an ACL injury?
ACL injuries most often occur when the knee is twisted forcefully, or hyper extended, causing the ligament to sprain or tear. ACL injuries may happen when landing from a jump, changing direction on the court, or even when colliding with another player.
What are the symptoms of an ACL injury?
For many who suffer ACL injuries, the initial injury is accompanied by a "pop" which is often felt and sometimes heard by the patient. Usually the knee will swell within 24 hours as the knee joint fills with blood and fluid. The swelling causes the knee to become stiff and painful and may last for several days. The pain and swelling will gradually decrease over the next few weeks, but athletes tempted to return to sports too soon may find that the knee gives way on their first attempt to pivot or change directions. This usually creates a sense of re-injury with more swelling, pain and stiffness.
How is an ACL injury diagnosed?
Physicians usually diagnose an ACL tear by physical examination of the knee. At times, physicians may order an MRI (magnetic resonance imaging) of the knee to confirm the diagnosis and to look for damage to the joint cartilage or other ligament damage.
What is the treatment for an ACL injury?
Unlike some injuries, the ACL doesn’t heal on its own once it is torn. In most active young people, surgical reconstruction of the ACL is recommended. Young patients with open growth plates should be treated in a way that gives close consideration to future growth issues. In immature patients, reconstruction of the ligament can be performed in a specialized fashion to preserve future growth around the knee. Long term studies have shown that without the ACL, the knee is susceptible to further cartilage damage with each new injury. This cartilage wear may lead to an increased risk of early arthritis. Before surgery is performed, the physician will often recommend rehabilitation to increase strength and range of motion while decreasing inflammation.
If surgery is not recommended, the patient is placed in a rehabilitation program to strengthen the knee and surrounding muscles. Exercises are provided in the program to help restore full range of motion. Once motion and strength have returned to normal, the patient will often return to limited activities with a brace.
What is the long term outlook for an ACL injury?
Surgical reconstruction of an ACL tear has proven to be very successful in recent years. Most athletes are able to fully return to sports without further knee problems. The rehabilitation process takes about 6 months to restore full functional strength so that sporting activities can be safely resumed.