Muscle strength exercises should be performed throughout the rehabilitation program. Each exercise should be performed until the muscles feel sore and fatigued, and then the next set should be performed after sufficient rest. Improvement in muscle strength is a key factor in restoring joint stability and should be maintained. The swelling of the knee joint will accompany the entire exercise process until the knee flexion and extension angles and muscle strength return to normal, then the knee swelling will gradually subside. If there is a sudden increase in knee swelling, the exercises should be adjusted and the amount of activity should be reduced, and the patient should return to the hospital for a review if necessary. Immediately after functional exercise, ice should be applied for 15-20 minutes. If the joint swelling, pain, and fever are usually obvious, ice can be continued 2 to 3 times a day. In general, patients can recover the function of the knee joint in four stages of rehabilitation; Stage 1: 1-7 days after surgery (postoperative edema period) Exercise program for the first week. Brace requirements: Knee brace locked in 0 degree extension position. You can walk on the ground with double crutches, and the affected limb is not weight-bearing; functional exercise: ankle active flexion and extension exercise (ankle pump): hard, slow, full range of plantar flexion and dorsiflexion activities of the ankle joint can promote blood circulation and eliminate swelling, which is important to prevent the emergence of deep vein thrombosis in the lower limbs. Daily 2 hours once, each time 1~2 groups, each group 20; isometric training: quadriceps isometric contraction, N cord muscle isometric contraction exercises; activity patella: push the patella up and down with hands, 4 times a day, each time 1~2 groups, each group 4 directions, each group 15; straight leg elevation training: after extending the knee, keep the knee straight, elevate until the heel leaves the bed at 10~15 cm, hold for 30~60 seconds /times; 3 sets of exercise per day, 20~30 times per set. Phase 2: 2~3 weeks postoperative (maximum protection period) Progress to phase 2 criteria: free control of quadriceps strength, able to do straight leg raise with relative ease; knee joint can be fully passively straightened; passive flexion and extension knee joint activity reaches 0~90 degrees; good patellar movement; knee swelling reduced; Week 2 exercise program: continue the above exercises on the basis of strengthening the terminal knee extension muscle strength Exercises: knee extension strength exercises in the range of knee joint near extension (0~20 degrees), 4 times a day, 1~2 sets of 20 each, with 2 minutes rest between sets; ankle plantarflexion training for resistance: toe press down hard against external resistance; knee mobility exercises: passive knee flexion 0~100 degrees, active knee flexion 0~80 degrees. Phase 3: controlled walking phase (4~6 weeks postoperatively) Criteria for progression to phase 3: active knee flexion and extension mobility 0~90 degrees; further reduction of knee swelling Exercise program in the 4th postoperative week: straight leg raise: resistance can be resisted, resistance gradually increased from 0.5 pounds (or 250 grams) to 5 pounds (2.5 kg); resistance training for hip adduction, abduction and posterior extension: resistance from 0.5 pounds ( 250 grams) gradually increased to 5 pounds (2.5 kg); micro-squat training (0-30 degrees), each lasting 30 seconds, 20 repetitions per group, 3 groups per day; weight-bearing and balance training: training under the guidance of a rehabilitation therapist. Partial weight-bearing training of the affected limb in the parallel bar (starting from 25%), weight shifting training forwards and backwards, left and right. Walking in the pool for 20 minutes; power bike training 15 minutes. 5-6 weeks postoperative exercise program: knee mobility training: passive knee mobility: 0~125 degrees, active mobility: 0~105 degrees; N rope muscle resistance training: resistance flexion of the knee joint; weight bearing and balance training: partial weight bearing training of the affected limb in the parallel bar (50%~100%), weight shifting training left, right and right, front and back. Stage 4: 7-12 weeks after surgery (mid-protection stage) Criteria for progression to stage 4: active knee flexion and extension 0~125 degrees; quadriceps strength loss ≤ 40% (Biodex measurement); N cord strength loss ≤ 20% (Biodex measurement); patients at this stage can walk completely off crutches. Phase IV exercise program: knee flexion and extension mobility: passive knee flexion and extension mobility of 0 to 140 degrees, active knee flexion and extension mobility of 0 to 120 degrees; strength training: single-leg heel lift training: 20 pieces/group; power bicycle resistance training: 15 minutes; squat training: 20 pieces per group, 3 groups per day; balance training: training single-leg stand on hard ground, or use balance Training on plates; training on up and down steps; hip trainer resistance training: forward flexion, back extension, abduction, adduction; Biodex isometric endurance training quadriceps strength (in hospital rehabilitation department); proprioceptive training (knee stability training); weight transfer training; backward walking training.