A full or partial tear in the anterior cruciate ligament (ACL), one of four ligaments critical to the stability of the knee joint.

An ACL tear is most often a sports-related injury. ACL tears can also occur during rough play, vehicle collisions, falls and work-related injuries. About 80% of sports-related ACL tears are “non-contact” injuries, commonly occurring when pivoting or landing from a jump. Female athletes are known to have a higher risk of injuring their ACL.

People who injure their ACL often complain of symptoms of their knee giving out from under them, and if torn, may have felt a “pop” at the time of injury. ACL tears cause knee swelling and pain. Your doctor can perform specific tests to look for signs of knee instability: the Lachman test, the dynamic extension test and the Pivot Jerk test. An MRI may also be used to confirm the tear.

Treatment may be conventional or surgical. Depending on your age, the extent of the disability, and your daily functional needs, an ACL tear may not require surgery. Rehabilitation, whether following surgery or not, focuses on restoring functional motion and strength, and improving the stability of the joint to prevent future injuries. Specific rehabilitation must focus on each individual athlete, and may last from twelve weeks up to six months.