Anterior cruciate ligament injury or rupture is one of the most common ligament injuries, many young people like soccer and basketball, there are many knee twisting movements, prone to anterior cruciate ligament injury. With the development of surgical techniques, ACL reconstruction surgery has been developed quite mature, but the preoperative and postoperative rehabilitation training are relatively weak, which is an important factor affecting the functional recovery of patients after surgery. After reconstructive surgery, the anatomical structure of the ligament is restored, and then the function of the ligament and the knee joint will be restored only by scientific training. After an ACL injury, elective surgery is usually chosen to be performed after the swelling of the joint has subsided. During this time, many patients are recuperating at home, without functional training. In fact, this is a very important time for rehabilitation. After an ACL injury, the quadriceps muscle on the injured side undergoes atrophy and loss of muscle strength, and then restoring muscle function is critical for later reconstructive functional recovery. Foreign studies have found that patients with better quadriceps muscle strength prior to ACL reconstruction have better postoperative functional recovery. The following are some methods of rehabilitation training after ACL injury. 1, joint mobility training: can be done in the supine position. Supine position, the knee joint slowly close to the hip, repeat 10-20 times per group, 2-3 times a day. 2, quadriceps isometric contraction training: daily isometric contraction of the quadriceps, that is, the leg is tensed, each time maintain 10 seconds, 10-20 times, 2-3 sets per day. 3, straight leg raise exercise: do four directions of straight leg raise, maintain 10 seconds and then slowly put down, 10 times in each direction. 4, squatting exercises against the wall: against the wall, slowly squat, maintain 10 seconds and then get up, repeat 10-15 times. 5, ice: after the injury that is, after training should be iced for 10-15 minutes.