ACL tears are one of the most common (and most well known) injuries of the knee, and are more common among athletes who participate in intense running and jumping sports. The cruciate ligaments are located in the knee joint connecting the femur (thigh bone) to the tibia (shin bone). Common causes for ACL injury include stopping running suddenly, incorrect landing, or direct impact (such as a football tackle).
A torn ACL is usually very painful, and accompanied by swelling. Patients often report a popping sound at the moment of injury, and their knee giving out. An untreated ACL tear can result in knee instability, and further damage to the knee joint.
Minor ACL tears can be treated with immobilization in a brace. More severe cases require ACL reconstruction surgery. For all cases, physical therapy is required to return the patient to full function.