Jeffrey V. DeLuca, MD
The anterior cruciate ligament (ACL) is the major stabilizing ligament of the knee. It is located in the center of the knee and runs from the femur (thigh bone) to the tibia (shin bone). The ACL can be injured by trauma or sporting events. Usually it is torn by a sudden direction change, twisting or hyperextending your knee. Sports associated with ACL tears are basketball, soccer, skiing and gymnastics. Female athletes are more susceptible to ACL injuries because of imbalanced thigh muscles, with stronger muscles at the front of the thigh (quadriceps), compared with those of the back of the thigh (hamstrings). Also limb alignment, joint laxity and a narrow notch (the tunnel at the end of the femur bone where the ACL runs through) may lead to an increased risk of ACL rupture for women.
Symptoms of an acute ACL injury include; a feeling of having a pop in the knee at the time of injury, significant swelling of the knee within hours of the injury and limited knee movement because of pain or swelling. Later, the feeling of instability or the knee giving out when walking can occur. If you experience any of these symptoms you should see an orthopedist right away.
The diagnosis of an ACL injury can be made by a physical exam, aspiration of blood from the knee and an MRI. Approximately 50 percent of all ACL injuries occur in combination with damage to the articular cartilage (the smooth white tissue that covers the ends of the bones), the meniscus (soft cartilage pads inside the knee) and other knee ligaments. These injuries can also be seen on an MRI.
The initial treatment of an acute ACL injury often includes ice, anti-inflammatory medication and physical therapy which help restore the movement and strength back to the knee. Non-operative treatment may be considered in older or sedentary patients, patients involved in non-pivoting sports such as biking, running and rowing, or in patients not able to participate in 6 months of a complete rehabilitation program. Surgical reconstruction should be considered if your knee is very unstable, you’re very active or want to resume heavy work, you want to return to pivoting type sports or if you have damage to other parts of your knee.
ACL reconstruction is outpatient surgery using arthroscopic techniques. The ACL tear cannot be sewn together, therefore a substitute graft needs to replace it. Graft options include your own patellar tendon or hamstring tendons which are used in younger patients or an allograft (cadaver) for patients over 40 years old. Post-operatively patients are started in physical therapy right away and use a leg brace and crutches until they gain adequate muscle strength and control so they can walk without them. Significant time and effort is required during the post-op rehabilitation to ensure an excellent result.
With an estimated 200,000 ACL related injuries occurring annually in the US and 100,000 ACL reconstructions performed year, ACL reconstruction is a very successful operation. 90% of patients have a favorable result with reduced pain, good knee function and stability and a return to normal levels of activity and sports.