The management of muscle atrophy two years after anterior cruciate reconstruction is based on ligament repair and muscle function. If the ligament repair is good and it is a simple lack of muscle strength, muscle strength training can be performed, if there is a problem with the ligament repair itself, clinical management is needed first. The method of muscle strength training is related to the existing muscle strength condition. If the muscle strength is so poor that it can only contract slightly or complete the full range of motion of the joint with counteracting gravity, electrical stimulation therapy or EMG biofeedback therapy is appropriate. It is more effective when combined with assisted active movement training. If the muscles are still strong enough to resist gravity or a certain amount of resistance, unarmed resistance training and resistance training with various equipment are appropriate. The most commonly recommended training movements for 0 ~ 45 ° half squat, 2 times a day, 15 minutes each time, and gradually transition to the full range of squatting exercises under protection. It should be noted that each plyometric exercise should cause some muscle fatigue; no significant recovery from overload will occur without significant fatigue, and excessive exercise can cause acute muscle strain. Pain that occurs during exercise should be considered a sign of causing or aggravating injury and must be avoided. Muscle atrophy two years after anterior cruciate reconstruction is recommended to consult a physician to determine the ligament repair, and rehabilitation needs to be completed under the guidance of a physician to avoid secondary injury.