The following methods should be based on their specific circumstances, either one of the most appropriate one. Generally practice 2 – 3 times a day, and strive for a slight increase in angle can be. The pulling sensation and slight pain around the muscles and joints during the exercise is normal, and the muscles should not be contracted against it, and should be completely relaxed, otherwise it will be ineffective. The weight of the load should not be too large, and the affected limb should be completely relaxed. If you have any special discomfort during or after the exercise, you should promptly inform your doctor or your therapist. There should be no rest in the middle, repeated flexion and extension, otherwise the effect will be affected. Rehabilitation training should follow the principle of gradual and orderly progress, do not be too hasty, and absolutely prohibit violence. Exercises for flexion: 1. Patellar luxation (can be started after stitch removal if the patella is not moving well): First find the edge of the patella, push the edge of the patella with your hand, and push the patella slowly and forcefully in the up and down direction to the limit position. Do this about 15 times in each direction, 2-3 times/day. This can be done before flexion exercises. 2, sitting (or supine) position leg hanging: sitting or lying on the bed, below the knee hanging outside the bed. The healthy leg under the affected leg to protect and relax the thigh muscles, so that the lower leg drops naturally, to the limit of protection for 10 minutes. If necessary, add a moderate load at the ankle joint, do not put the load on the back of the foot. 3.Sitting position “top wall”: sitting on the chair, the affected side of the toe against the wall or fixed, slowly move the body forward to increase the angle of bending the knee, feel the pain and keep still, a few minutes after the pain disappears or lower, and then move forward to the limit. The whole process is controlled within 30 minutes. 4, prone knee flexion: prone position (face down on the bed), natural extension of the legs, hold the affected leg ankle joint, so that the knee joint flexion (available long towel or wide band tied to the ankle to facilitate pulling). Or with the help of another person, perform active flexion and extension exercises after each passive flexion: Sit with the foot not leaving the bed. Slowly and forcefully, flex the knee to the maximum, hold for 10 seconds and then slowly straighten. 10-20 reps/group, 1-2 groups/day. Exercises for knee extension: 1. Sitting or supine knee extension: Sitting or supine, feet elevated, knee suspended, load above the knee, but do not place the load directly above the patella. Relax the muscles completely and hold for 30 minutes. 1-2 times/day. 2, prone suspension: prone, below the knee hanging outside the bed, pay attention not to put the patella on the edge of the bed, the ankle joint weight. Requirements as above.