From time to time in clinical work, patients ask questions about methods of lower extremity muscle training and joint mobility exercises. In my opinion, this is very important for knee lesions, both preoperatively and postoperatively. Good knee function should involve movement under stable conditions, meaning that the joint should be able to move (that is, the joint should be mobile enough) and that the joint should be stable enough. Many knee injuries destroy stability, and over time, joint adhesions can occur, resulting in decreased mobility. Surgery after a knee injury is usually performed to restore joint stability, such as cruciate ligament reconstruction and lateral collateral ligament repair. After surgery, the knee joint is not able to move normally in the early stages to protect the surgical result and post-operative pain, which can result in joint adhesions and a decrease in joint mobility. After a knee injury or early surgery, the muscles of the lower extremity, especially the muscles in front of the thigh (the quadriceps), will atrophy quickly because the lower extremity cannot move with normal force and full joint range of motion. Usually one month after injury or surgery, the quadriceps muscle atrophies significantly if effective functional exercise is not performed. Normal muscle function is very important to maintain the stability of the knee joint, especially during sports. Therefore, proper muscle strength and joint mobility exercises are exceptionally important for restoring joint function, both after injury and after surgery. With regard to quadriceps muscle training, we attach great importance to strength and frequency, which means that we need to exert enough force each time until the muscles are sore, and enough times to achieve the purpose of muscle strength training. Quadriceps muscle strength training methods are: 1, tense leg exercise: knee straight case, force the quadriceps muscle tense, for 5 to 10 seconds to feel muscle soreness and then relaxation is counted once a day to practice 3 to 5 groups, each group practice 15 to 50 times. This is the first level of muscle strength training exercises, anesthesia can be carried out after waking up, can be throughout the rehabilitation period. 2, straight leg raise exercise: lying down, knee straight, lower limbs raised, about 40 ° with the bed, for 5-10 seconds to feel muscle swelling and then relaxation is counted once, 3-5 groups per day, each group of 15-50 times. This is the second level of muscle strength training exercises, the second day after surgery, muscle strength recovery level 3 or more to carry out. Attention is: lower limbs should be lifted quickly and slowly, not to fall suddenly; lower limbs should not be lifted too high, and not to do knee extension and flexion in the air. 3, single-leg standing exercises: try to straighten the knee joint, standing with the affected limb, 1~3 minutes each time, 3~5 times a day. This is a tertiary exercise of muscle strength training, which can only be performed if the patient can easily complete the straight leg raising exercise, requiring the muscle strength of the quadriceps muscle to recover to grade 4+. Patients with fork ligament reconstruction usually start this exercise 1 week after surgery. Note: Patients with fork ligament reconstruction and meniscal sutures should wear the brace securely before getting out of bed to do this exercise. With regard to knee mobility exercises, we place a lot of emphasis on improving the mobility of the joint with each exercise, rather than on the number of times and the speed of the joint movement. Knee mobility exercises include: ① Patella pushing exercises: avoiding patellar adhesions is important to prevent knee adhesions, the patient himself or a chaperone should pinch the patella with both hands and do up and down and inside and outside activities in four directions, with the range of patellar activities on the opposite side as a reference, 3~5 groups per day, 5~15 times per group. ② Bedside leg hanging exercise: the patient does bedside, the affected limb naturally relaxes and hangs down, insist on 1~3 minutes to count once, practice 3~5 times a day. This exercise is the first level of joint mobility exercise, which is a passive knee activity and is suitable for use in the early postoperative period when the joint mobility is not yet greater than 90°. Note that the patient should be protected from lying down to the bedside, and the patient’s heel should be protected after reaching the bedside to gradually make the affected limb droop. ③Knee lifting exercises in bed: In bed, the nurse should hold the knee joint upward with both hands in the N fossa, so that the knee joint is flexed, and then slowly straighten the knee joint after releasing the hands. 3~5 sets per day, 5~10 times per set. This exercise is a level 1 exercise for joint mobility, which is a passive knee activity and is suitable for application within 2~4 weeks after fork ligament reconstruction and meniscus suture surgery. ④ Prone pull-back exercise: The patient is in prone position, with a wide cloth belt or elastic band wrapped around the back of the foot, and the patient himself pulls the foot of the affected lower limb toward the hip to flex the knee joint. Each time the knee joint is flexed to the maximum degree, so that the patient has a sore feeling in the knee joint, hold for about 1 minute. Perform 3 to 5 sets of 1 to 3 times per day. This exercise is a secondary exercise for joint mobility, which is a passive knee activity and is suitable for patients whose knee mobility is already greater than 90°.