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The anterior cruciate ligament (ACL) is one of the four major ligaments of the knee. Ligaments are strong, dense structures made of connective tissues that help stabilize a joint. In this case, the ACL connects the femur to the tibia and helps provide stability to the knee and minimize stress across the knee joint. Twisting or pivoting movements can often cause the ACL to strain or tear.
ACL tears occur in athletes participating in cutting and pivoting sports such as basketball, football, soccer, and skiing. At the time of an ACL injury the athlete typically feels a “pop” or a tearing sensation. This is followed by swelling within the first six hours of the injury. The most common injury associated with ACL tears is a meniscus tear.
It is well recognized that ACL injuries are much more common in females. There are multiple reasons for this including bony anatomy, hormonal differences, muscular balance, and the way they perform certain sports. Of these factors the ones we can potentially change are muscular balance and the way sporting moves are completed. Females tend to cut and jump with their knees only slightly bent, which can predispose them to ACL injury. The hamstring to quadriceps strength ratio is also different from males. Studies have shown that strengthening exercises and plyometric programs aimed at changing these factors can prevent ACL injuries.
ACL strains can sometimes be treated with physical therapy and muscle strengthening. However, most complete tears require surgery in active patients. Modern ACL surgery involves completely removing the torn ligament and reconstructing the torn ACL. The most common grafts used to reconstruct a torn ACL are the patella tendon, hamstring tendons, or cadaver tissue (allograft). Each graft offers specific advantages and disadvantages, so it is important to understand the differences.