Cruciate ligament injuries of the knee are one of the most common and serious sports injuries. There is an increasing emphasis on the mechanical function of the cruciate ligament and a growing awareness of its impact on the stability of the knee joint after injury. If not treated in a timely manner, the knee joint may not be able to meet the needs of daily life and sports and may cause a series of sequelae in the knee joint, so surgery should be performed to reconstruct the ligament and its function. Along with the maturity of knee arthroscopy, arthroscopic cruciate ligament reconstruction has become more popular. However, post-operative rehabilitation has always been a problem for patients. Some patients even fail the surgery because they do not know how to exercise. Here I will give you an introduction of how to perform postoperative exercises. I hope it can help patients to recover after surgery. Wang Wen, Department of Orthopaedic Trauma, Jinan Military General Hospital, should wear an adjustable brace after surgery. For the first 6 weeks after surgery, except for practicing joint flexion, the knee joint should be fixed in the extension position with the brace. The position chosen for knee exercises is: lying down with the lower limb flat on the bed, making sure that the brace is firmly fixed and a soft pillow is placed under the knee joint. On the first postoperative day, the ankle joint was flexed and extended with force, slowly and with full range of motion. Tense and relax the anterior thigh muscles for 5 seconds, then relax for 2 seconds, then press down on the pillow. The exercise should be performed at least 1000 times. In subsequent exercises, if knee flexion and extension exercises are not performed, the exercise should also be maintained at greater than 1,000 reps/day, and straight leg raising exercises should be performed on the second postoperative day. Keep the knee straight during the exercise, lift slowly and stay for 5 seconds after lifting. Exercise as many times as possible according to your situation: more than 10 to 40 times/group, more than 10 to 50 groups/day. The standard is to feel the soreness of the thigh on the second day. On the third day after surgery, perform lateral leg raising exercises, more than 10 to 40 times/group, more than 10 to 50 groups/day. The above is mainly to perform muscle strength exercise, in the following days to continue to perform straight leg raising training and side leg raising exercises every day. The ultimate goal of the exercise is to achieve bilateral thigh equal thickness. The improvement of muscle strength is the key factor of joint stability. The atrophy of thigh muscles after cruciate ligament injury seriously affects joint stability and surgical effect, so it must be practiced carefully. Muscle strength exercises should be concentrated until the muscles have a sense of soreness and fatigue, and then proceed to the next group after sufficient rest. The rest of the body parts (such as the upper limbs, waist and abdomen, and the healthy side leg) should also be practiced as much as possible to improve the physical quality and promote the recovery of the surgical local. The presence of pain during functional exercises is unavoidable. If the pain can subside to the original level within half an hour after the exercise is stopped, no damage to the tissue will occur and the exercise should be continued. Swelling of the joint will accompany the whole exercise process and is normal. Flexion and extension of the knee joint training instruction knee flexion with the change of the angle of the brace, the activity in place can be. Subsequent activities to the prescribed angle 3 times a day. In addition to practicing the flexion function of the joint, the brace is fixed in the knee extension position. The adjustment angle and time scheme of the brace should be adjusted weekly according to the following angle requirements and to the prescribed angle. Week 1: 10°, Week 2: 30°, Week 3: 60°, Week 4: 90°, Week 5: 120°, Week 6: Full range of motion weight-bearing exercises. 4 weeks later, you can stand on straight legs with the protection of a brace, but the weight of the affected limb should not exceed 50% of your body weight. 3 months later, you can be fully weight-bearing, but you should wear a brace for protection, and sleep without a brace. At the same time, squatting exercises: back against the wall, hip flexion and knee flexion 50°, lower leg perpendicular to the ground, feet shoulder-width apart, toes and knees forward, 2 minutes / time, according to their own situation, the more times to exercise the better. 6 months later, remove the brace, normal walking. Begin single-leg semi-squatting knee exercises on the affected side. The affected leg stands on one leg with the upper body straight, slowly squats, and then slowly stretches until it is completely straight. Requires slow, hard, controlled (no swaying). Return to normal work, training or sports after 1 year.