Anterior Cruciate Ligament (ACL) Tear of the Knee
What is an ACL tear of the knee?
ACL tears are one of the most common knee ligament injuries. The ACL runs diagonally in the middle of the knee. It connects the back of the femur (thighbone) to the front of the tibia (shinbone) and helps stabilize the knee from rotating. Injuries range from mild, small tears, to severe tears when the ligament and part of the bone separate from the rest of the bone. Most ACL injuries are complete or near-complete tears.
How does an ACL tear occur?
An ACL tear is most often a sports-related injury. Athletes who play sports that involve running, pivoting, turning and jumping are especially susceptible. They may feel a slip or pop in their knee and the knee gives out from under them. ACL tears are extremely common in young women athletes, and often occur together with injuries to the meniscus (approximately 50% of the time)
It will be impossible to prevent ACL tears in cutting sport athletes. However, newer injury prevention programs focusing on core strengthening and improved exercises to help improve knee rotational control and proper muscle recruitment appear to reduce ACL injury.
What are the symptoms of an ACL tear?
People who suffer an ACL tear may hear a loud pop at the time of their injury or feel a sudden shift in their knee joint in association with a pivot, deceleration change of direction maneuver. Pain ranges from mild to excruciating, depending on the amount of bleeding and swelling associated with the injury.
Other symptoms include:
- Knee swelling and stiffness
- Instability in the knee joint
- Limited range of motion
- Discomfort while walking
- Tenderness along the joint line
Often the initial pain and swelling resolve with time. If you attempt to return to cutting sports without any treatment, however, you risk causing further damage to your knee, particularly damaging the meniscus and the cartilage surfaces of the joint.
How is an ACL tear diagnosed?
In addition to a history and physical exam, MRI is the most effective test to confirm the diagnosis of a torn ACL. Often times, the diagnosis is obvious by history and physical exam that MRI is not needed. Xrays should always be performed to rule out fractures that can occur with ACL tears.
What is the treatment?
ACL tears do not necessarily require surgery. Initial treatment focuses on pain control and restoring range of motion. It is important to regain motion in the knee as soon as possible to prevent permanent damage.
Surgery depends on several factors including a patient's age, activity level, severity of symptoms and expectations. For older patients who are stable, with little desire to return to high-level sports or fitness routines, non-operative rehabilitation and activity modification may be sufficient. For active patients – young athletes especially – reconstruction is highly recommended. Stable knees are crucial for returning to sports and preventing re-injury.
ACL reconstruction surgery uses an autograft (tissue from your body) or an allograft (tissue from a cadaver) to replace the ligament. Following surgery, proper rehabilitation is critical. Patients should wait from 6 to 9 months before returning to aggressive contact sports. The time is important for the maturation of the tendon becoming a ligament (ligamentitization).