1. Anatomy of anterior cruciate ligament: the anterior cruciate ligament starts from the medial side of the femoral epicondyle facing away, forward and medially oblique, and ends at the medial side of the intercondylar spine of the tibial plateau. 2, ACL function: prevent tibial anterior displacement; control knee rotation; control knee internal and external rotation; prevent knee hyperextension; have proprioceptive function. 3, ACL injury mechanism: valgus injury; valgus injury; hyperextension injury 4, ACL clinical manifestations: joint instability symptoms: can not stop and turn sharply; afraid to jump with the affected limb; can not run fast, jogging, fast walking. Symptoms caused by concurrent injuries: for example, concurrent meniscal injury causes knee pain, interlocking; knee synovitis can cause knee swelling; late stage involving cartilage injury can cause walking pain, serious after the need for total knee replacement surgery, after the study of ACL injury can be formed ten years after osteoarthritis. 5, ACL clinical examination: positive anterior drawer test; positive Lachaman test. 6, the importance of ACL reconstruction: reconstruction of the ACL can restore the stability of the knee joint, relieve the symptoms of instability, and prevent the occurrence of secondary injuries, early reconstruction, the situation of secondary injuries is greatly reduced. 7. ACL reconstruction: autologous tendon; allograft tendon; autologous + allograft tendon. 8, ACL postoperative rehabilitation: postoperative knee extension brace fixed (including sleep), strengthen the quadriceps contraction and straight leg exercise; 3 days after surgery can start passive knee flexion exercises, wear knee extension brace when getting out of bed to support the crutches part of the weight walking; brutal January passive knee flexion does not exceed 90 degrees; full 6 weeks can be weight walking, full 3 months to remove the knee extension brace; full 6 months to start jogging; full 1 year to gradually resume Sports.