The knee joint is the most damaged joint in sports, so it is very important to protect our knee joint. The muscles around the knee joint are strong enough to protect and cushion the knee joint during activities. Among the muscles, the most protective of the knee joint is the quadriceps. The quadriceps is the most important muscle group in the human thigh. It maintains the stability of our knee joint, especially the patella and the anterior-posterior stability of the knee joint, and is the main force when we walk, go up and down stairs, squat and other movements. Exercises for the quadriceps not only maintain the normal function required for our daily life, but also enhance the knee joint protection and motor function for people suffering from knee disorders and promote the recovery from knee injuries. On the knee exercise methods, the most commonly used are the following: a. static squatting exercises back against the wall, feet apart, shoulder-width apart, gradually stretch forward, and the body’s center of gravity to form a certain distance, about 40 to 50 centimeters. At this point the body has simultaneously presented a squatting posture, so that the lower leg is perpendicular to the ground. The angle between the thigh and calf should not be less than 90 degrees. Because the squat is too deep, it will significantly increase the pressure on the patellofemoral joint, but also does not produce a strong exercise effect on the thigh muscle strength. Gradually increase the amount of exercise from just a few dozen seconds to a few minutes. This requires what we call the three-star connection. Second, tense leg exercise That is, when the knee is straight (sitting, standing, lying can do) active contraction of the quadriceps muscle, make it tense, hold for 5 seconds, and then relax for 2 seconds, so repeated. It is best to do enough 2000 times a day. It is not required to do it all at once, it can be done in several times, with the same effect. Step 1: straight leg raise exercise: straight leg raise Lie on the bed, straighten the bit will lift the whole leg, let the angle between the leg and the bed in about 30 degrees is best. Hold for 5 seconds, then put down for 2~3 seconds, and so on repeatedly. Do 3~4 sets per day, each set of exercises effective indicator is the muscle feel enough fatigue, you can rest 1-2 minutes. You can gradually increase the weight of the legs, strapped to a sandbag in the legs. Step 2: Knee extension resistance Sit on the edge of the bed or chair, from the relaxed bent knee position until the straight knee joint. Of course, the most important exercise for effective medial range of motion is within 30 degrees of near extension, so if the focus is on the medial side, just work mainly on the last 30 degrees. The exercise requirements are the same as for the straight leg raise. But it should be noted that, because the essentials of the exercise, intensity is not easy to grasp, we are in the above exercise, it is best to carry out under the guidance of a doctor to play the maximum effect of exercise to avoid sports injuries. Third, heel lifting exercises can be done at home or in the unit can be completed, hands holding the support to prevent falls, the forefoot of both feet stand, and then repeatedly do heel lifting action. You can also stand on the special standing heel lift frame for practice.