The knee is the largest joint in the body and consists of the femur (thigh bone), patella (knee cap) and tibia (shin bone) each covered in cartilage, a smooth and slippery material that helps bones glide and move without pain. In addition, the knee has two pieces of ring-shaped cartilage that act as “shock absorbers” for the knee during activities, called the lateral and medial meniscus. The bones and menisci are stabilized by four important ligaments that support the knee: the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL). The ACL is one of the cruciate ligaments, is the most commonly injured ligament, and prevents the tibia (leg) from gliding forward (anteriorly) with respect to the knee and the femur.
Injuries to ligaments, such as the ACL, are called “sprains” and occur during specific athletic activities. This may include cutting maneuvers that involve changing direction, suddenly stopping or jumping, or being tackled in football or slide-tackled in soccer. Female athletes are at higher risk for ACL injuries than male athletes for unknown reasons, however some evidence suggests this may be related to conditioning, muscular strength, or variations in anatomy and alignment.
ACL injuries can be classified as Grade 1, 2, or 3. A grade 3 injury is a complete rupture and results in pain and swelling within 24 hours. As swelling and pain decrease you may have an unstable knee which has symptoms of “giving out” during normal activities. These types of injuries may require surgical reconstruction.
Injuries to the ACL can be treated non-surgically with physical therapy for muscle strengthening and bracing for external support. However, for active patients, physical therapy may not provide enough knee stability. The ACL cannot be “stitched back together” and instead must be replaced (reconstructed). This is typically done with a graft either from the patient (autograft) or from a donor (allograft). Various graft choices are available, and these options should be discussed with your surgeon. In addition to various graft options, different techniques can be used to reconstruct the ACL, and the specifics of each should be discussed with your surgeon.
Rehabilitation will play a critical role in returning you to normal activity and getting the best results from your new ACL. Participating in your surgeon’s recommended pre- and post-surgical protocol is very important. Physical therapy will focus on strengthening the surrounding muscles, stabilizing your joint, increasing motion to your knee, and reducing pain. Exercises should be performed in a supervised setting, as well as at home on your own time. Your commitment to rehabilitation is key to a successful outcome.