Communicate with the surgeon at any time during the rehabilitation process to ensure safety. (I) Initial period (0-1 week after surgery) 1. On the day of surgery: After the anesthesia subsides, start to move the toes and ankle joint. (1) Ankle pump – forceful, slow, full range flexion and extension of the ankle joint, 5 minutes/group, 1 group/hour. (2) Quadriceps isometric exercises – i.e. thigh muscle tensing and relaxation. Should be done as much as possible without increasing pain. (3) N rope muscle isometric exercise – the affected leg force down the padded pillow, so that the back of the thigh muscle tense and relaxed. The requirements are the same as above. All exercises should be done as much as possible without increasing pain! (4) 24 hours after surgery, you can walk on the ground with the help of crutches, but only to go to the toilet and other necessary activities. (2) Day 1 after surgery: (1) Continue the above exercises. (2) Change the ankle pump to anti-gravity exercises. (3) Start straight leg lift – straight leg lift after knee extension to 15M heel from bed, hold for 5 seconds. 30 times/group, 3-4 groups/day. (4) Start side leg raise exercise, same requirements and times as above. (5) Start the back leg raise exercise, prone, straight leg raise after knee extension to the toe 5M from the bed, hold for 5 seconds. The requirements and the number of times are the same as above. (6) Weight bearing and balance: separate the feet under protection and move the center of gravity alternately from side to side within the range of slight pain. 5 min/time, 2 times/day, separate the feet back and forth and move the center of gravity. If the pain and swelling are not obvious, you can support the single crutch or go down without crutch, but do not encourage more walking. 3. Postoperative day 3 （1） Continue the above exercises. (2) Begin flexion exercises, to the extent of slight pain, to reach the largest possible angle. 4. Postoperative day 4: (1) Continue the above exercises. (2) Start single-leg standing balance exercise. 5 minutes/time, 2-3 times/day. (3) Begin prone “leg hook exercise”, 30 times/set, 2-4 sets/day. (4) Active knee flexion up to 90 degrees. 5. Postoperative day 5: (1) Continue and strengthen the above exercises. (2) Start active extension and flexion exercises within 0-45 degrees of weight bearing in standing position. 30 times/group, 2-3 groups/day, ice for swelling and pain after the exercises. 6. Postoperative week 1: (1) Active flexion greater than 90°. (2) Can stand on one foot, can walk short distances without crutches. (3) Start squatting exercises against the wall. Squatting exercises: back against the wall, feet shoulder-width apart, toes and knees forward, no “internal and external figure of eight”, gradually increase the angle of squatting (less than 90 °) with increasing strength, 2 minutes / time, interval of 5 seconds, 5-10 consecutive / group. 2-3 groups / day. (4) Begin standing “leg hook” exercises, resisting flexion to the maximum pain-free angle for 10-15 seconds. 30 times/group, 4 groups/day. (2) Early stage: (2 weeks to 1 month after surgery) Purpose: To strengthen mobility and muscle strength exercises: to improve joint control and stability; to start to resume daily activities. With the improvement of muscle strength level, exercises to improve absolute strength are the main focus in this period. Choose a medium load (the amount of load to complete 20 movements that is fatigue), 20 times / group, 2-4 groups of continuous exercises, rest 60 seconds between groups, until fatigue. Care should be taken to control the amount of exercise to avoid joint swelling and fluid accumulation. If the joints feel swollen and hot after the exercise, ice should be applied in time! 1.Week 2 after surgery: (1) Active flexion to 120-130°. (2) Intensive muscle strength exercises. (A straight leg raise can last up to 6 minutes.) (3) If the joint is not significantly swollen or painful, walk with a normal gait as much as possible. (4) Begin to instruct the thigh hamstring resistance exercises in the knee extension position. The load, angle, number of times and duration of the exercises should be determined according to your condition. Generally, 30 times/group, 2-4 groups/day. 2. Postoperative week 3: (1) Passive flexion to 140°. (2) Intensify muscle strength exercises. (3) Start anterior-posterior and lateral straddle exercises with gradual transition and increasing load. 30 reps/set, 4 sets/day. (3) Mid-term: (1 month-2 months after surgery) Purpose: To strengthen joint mobility training to the same level as the healthy side; to strengthen muscle strength training and improve joint stability; to restore the ability to perform various activities of daily life and light exercise. 1. Postoperative week 5: (1) Active flexion up to 150° (full range, same as the healthy leg), and basically pain-free. (2) Start the 45-degree half-squat exercise on the affected leg. 5 minutes/time, 4 times/day. (3) Start fixed bicycle exercise. 30 minutes/time, 2 times/day. 2.Weeks 6-8 after surgery: (1) The active flexion and extension angle reaches the same as the healthy side, and there is no pain. (2) Can complete daily activities, such as walking up and down stairs, riding a bicycle, walking more than 5000 meters without swelling and pain in the joint. (3) Begin kneeling exercises. (4) Begin pedaling exercises. (5) Start swimming, rope skipping and jogging. (4) Late stage: (2 months-3 months after surgery) Purpose: To fully resume all activities of daily life. Strengthen muscle strength and joint stability. Gradually resume exercise. Increase the maximum strength, choose a large load of 70% 1RM (complete 12 movements that is the fatigue of the load), 8-12 times / group, 2-4 groups of continuous exercises, rest 90 seconds between groups, until fatigue. 1.Start the knee ring exercise. 2.Start jumping up and down exercises. 3.Start lateral straddle jump exercises. 4.Mobilize and start the basic movements of the special exercises. If necessary, wear knee pads for protection. (E) Recovery period: (3 months after surgery) Purpose: To resume full-scale sports or strenuous activities. 1. Gradually resume strenuous activities, or special training. 2. Strengthen muscle strength and joint stability in running and jumping. 3, muscle strength test, the affected muscle strength up to 85% of the healthy side or more, no pain during exercise, no obvious swelling, then can fully resume sports.