The cruciate (or crossing) ligament stabilizes the knee. The anterior cruciate (ACL) may completely break (rupture) when the knee is bent beyond its normal range of motion or with excessive twisting. Signs and symptoms include a ‘pop’ sensation with significant swelling and pain. There is a sense of instability or the knee giving away. Initial treatment includes rest, ice, elevation, and compression. Physical therapy consisting of progressive strengthening and functional exercise may facilitate recovery. If knee instability persists, surgery is indicated. The middle third of the patellar tendon, hamstrings, or cadaver ligament may be used to reconstruct the lost ligament.

ACL tears are common in teenage female athletes. Some of the best clinical/sports medicine research to date, suggests that a preventive training program can significantly reduce the risk of ACL injuries in female adolescent athletes.