The quadriceps is a group of muscles that move the knee joint, it starts from the thick line of the femur of the anterior inferior iliac spine and ends at the thick tibial ridge, it consists of the rectus femoris, medial femoris, middle femoris, and lateral femoris respectively, it is the extensor muscle of the knee joint, its tension is three times stronger than the flexor muscle. The quadriceps is mainly a uni-articular muscle, with patellar enlargement, and the vertical distance of the knee flexion and extension axis of motion, its moment is much larger than that of the knee flexor, and the leverage is strong; while the knee flexor is mostly a bi-articular muscle, its tension factor affects the leverage, the role of the quadriceps has the following 3 aspects: 1, straighten the knee joint; 2, the contraction of the quadriceps during knee flexion can fight gravity and maintain the stability of the knee joint; 3, maintain the stability of the knee joint. 3. to maintain dynamic stability during knee movement. The attachment position of the medial femoral muscle is lower than that of the lateral femoral muscle, and its fiber direction is more oblique, thus playing an important role in stabilizing the patella. The medial femoral muscle also allows external rotation of the tibia during the last 10°-15° of knee extension to enhance the knee joint snapping mechanism. Therefore, strengthening of the quadriceps helps to protect the knee joint because, as an important tissue structure for functional stability of the knee joint, the quadriceps can relieve the impact of sports on the knee joint, and when the toes land in normal gait, the contraction of the quadriceps plays a cushioning role against the impact of landing, reducing the weight and stress on the joint. Quadriceps training can improve its role in regulating the weight-bearing condition of the knee joint; strengthening quadriceps training can improve the stability of the knee gait. Therefore, quadriceps exercise has a therapeutic effect on osteoarthritis of the knee.