With the widespread popularity of mass sports, the number of sports injuries is increasing, among which anterior cruciate ligament (ACL) injury is one of the common injuries, with post-injury joint pain and poor stability, which seriously affects the normal functional activities of patients’ knee joints. Without early repair, different degrees of knee instability often remain, and unstable joints are prone to repeated injuries, leading to traumatic arthritis and wasting atrophy of the corresponding muscles, so arthroscopic anterior cruciate ligament reconstruction is an effective treatment method. However, postoperative patients do not cooperate with functional exercises, which can lead to the reconstructed ligament being lax or stretched, or even ruptured, and not able to play its proper role, seriously affecting the surgical effect. Therefore, functional exercises for patients after ACL reconstruction is a very important therapeutic measure, which directly affects the therapeutic effect. The pain that exists in performing the functional exercises of this program is unavoidable. If the pain subsides to its original level within half an hour of the cessation of the exercise, there is no damage to the tissue and it should be tolerated. Plyometric exercises should be concentrated until the muscles feel sore and fatigued, and adequate rest should be taken before proceeding to the next set. The number of exercises, time, and load depends on your own situation, and the healthy side should be practiced at the same time. Improvement of muscle strength is the key factor of joint stability, and must be practiced carefully. In addition to the surgical limb braking protection, the rest of the body parts (such as the upper limb, waist and abdomen, the healthy side of the leg, etc.) should be practiced as much as possible to ensure the physical quality, improve the overall circulatory metabolism level, and promote the recovery of the surgical localization. Early joint mobility (flexion and extension) exercises should be performed only once a day, aiming to improve the angle just enough to avoid repeated flexion and extension, and multiple exercises. It is more important to practice according to the prescribed angle, neither advance nor push back. If the flexion angle does not improve for a long period of time (>2 weeks), there is a possibility of joint adhesion, so it is important to pay attention to it and insist on completing the exercises, or directly ask the doctor for help. Apply ice for 15-20 minutes immediately after mobility exercises. If the joint is usually swollen, painful and warm, ice can be applied again, 2-3 times a day. Swelling of the joints will accompany the entire exercise process, swelling does not increase with the angle of the exercise and the increase in activity is a normal phenomenon, until the angle and muscle strength basically return to normal swelling will gradually subside. If the swelling increases suddenly, you should adjust the exercises and reduce the activity level, and if it is serious, you should go to the doctor in time. I. Early – inflammatory response period (0-1 weeks) (i) the day of surgery: after the anesthesia subsides, begin to move the toes, ankle joint; if the pain is not obvious, you can try to contract the quadriceps muscle. That is, tensing and relaxing the anterior thigh muscles. (ii) Postoperative day: 1. Ankle pump – forceful, slow, full range flexion and extension of the ankle joint. No time is specified for ankle flexion and extension exercises, which can be performed while reading newspaper, watching TV, reading a book or resting in bed, the more the better, which is important for promoting circulation, reducing swelling and preventing deep vein thrombosis. 2, quadriceps (anterior thigh muscle group) isometric exercises – that is, thigh muscle tensing and relaxation. Do as many as possible without increasing pain. (greater than 500 times/day) 3, the first postoperative day you can walk on the ground with the help of crutches, but the affected leg should be protected under the splint, with the help of crutches, and the affected limb is not weight-bearing. (iii) 2-7 days after surgery: remove the drain, if no drain is placed in the joint, and the postoperative joint swelling is severe you can consider arthrocentesis to extract the accumulated blood. 1.Continue the above exercises. 2. Ankle pump exercises are the same as the first day after surgery. 3, start to try straight leg raising – straight leg raising after extending the knee until the heel is 15M from the bed, hold until exhaustion. 2-3 times/day. The pain at the surgical incision during the exercise is normal and should be tolerated. Special attention should be paid to the exercise: before starting to lift the leg, the muscles in front and behind the thigh should be tensed, so that the whole leg forms a whole under the protection of the muscles, and the knee joint should be ensured to be completely straight, and then lift the leg, so as to prevent the ligaments that have just been reconstructed from being loosened when the leg is lifted straight up. 4, start side leg raising exercises, 10 times / group, 2 groups / day, you can carry out a group in the morning and afternoon. 5.Walking on the ground with crutches, but the affected leg should be protected under the splint, with crutches, and the affected limb is not weight-bearing. Second, the initial period: (2-3 weeks) strengthening muscle strength exercises (straight leg lifting up to 6 minutes) Third, the middle period: (4 weeks – 3 months) (a) 4 weeks after surgery: (sleep without splint) 1, passive flexion up to 90 °. 2, at this time, the affected limb should still not be fully protected by crutches, but the affected leg should be protected by crutches, without weight bearing. 2, at this time, the affected limb still do not fully weight-bearing, walking with crutches, the affected limb weight-bearing one-third. 3.Active splint can be changed to 0-60° range. (B) 5 weeks after surgery: 1, passive flexion up to 100 °. 2, at this time the affected limb should not be fully weight-bearing. 2, at this time, the affected limb should not be fully weight-bearing, walking with crutches, and one-third of the weight-bearing of the affected limb. 3.Active splint can be changed to in the range of 0-90°. (ii) 6-9 weeks postoperatively: 1, passive flexion angle 110° at 6 weeks postoperatively, knee flexion to 120° at 7 weeks postoperatively, knee flexion to 130° at 8 weeks postoperatively, and knee flexion close to the maximum angle of the normal contralateral leg at 9 weeks postoperatively. 2. Start full weight bearing at 6 weeks postoperatively. 3.Strengthen muscle strength and increase straight leg raising exercises. 4, Start static squatting exercises. 5.Move the splint to maintain the range of 0-90°. (iii) 10 weeks-4 months postoperatively: (Splint can be removed) 1, Active flexion and extension of the knee angle is basically the same as that of the healthy side, and there is no obvious pain. 2, daily prone position flexion so that the heel touches the buttocks, continuous stretching 10 minutes / times. 3.Start kneeling exercises. 4.Start pedaling exercises, but do not do any knee extension exercises and knee flexion exercises against resistance. 5.It is better not to run at this time, running until after 5 months after surgery, but you can walk fast at any speed. Fourth, the later stage: (5 months – 6 months) Purpose: a full resumption of daily life activities, but jogging until 5 months after the operation. Strengthen muscle strength and joint stabilization. Gradually return to sports. In the later stage, increase the maximum strength, choose the large load (the load of fatigue when completing 12 movements), 8-12 times/group, 2-4 consecutive groups of exercises, rest 90 seconds between groups, until fatigue. 1.Starting the knee loop exercise. 2. Start jumping up and down exercises. 3.Start lateral jumping exercises. 4.Begin swimming (breaststroke is prohibited in the early stage), jumping rope and jogging. 5.Athletes start the special practice of base movements. 6.To make the muscle strength of the operated knee reach more than 85% of the good leg before the end of 6 months after the operation. During this period, the reconstructed ligaments are not yet strong enough, so the exercises should be gradual and should not be forced or blindly advanced. And should strengthen the muscle strength to ensure the stability and safety of the knee joint in sports, if necessary, can wear knee pads to protect, but only advocate the use of strenuous exercise. V. Recovery period: (7 months – 1 year) Purpose: full recovery of sports or strenuous activities (prerequisite: the muscle strength of the operated knee joint reaches more than 85% of the good leg, or else we should postpone strenuous sports). Strengthening of the muscles and stabilization of the joint during running and jumping. Gradually resume strenuous activities, or specialized training. If the mobility of the affected joint reaches normal, and the muscle strength reaches 85% or more of the healthy side, then you can fully resume sports.