Anterior Cruciate Ligament (ACL) plays an important biomechanical role for the stability of knee joint. ACL injury often leads to injuries of articular cartilage, menisci, or other supporting structures, and subsequent development of degenerative arthritis. Controversies still exist in the best treatment modalities of ACL injuries. hut the author considers it most important to make the appropriate patient selection for operative reconstruction or nonoperative treatment. and describes the treatment principles of ACL injury, including diagnosis, patient selection and the treatment modalities for successful treatment of ACL injury.