Pain in the knee when the patient’s leg is flexed is due to a significant increase in local intramuscular pressure in the patient’s knee joint in flexion, which produces a large amount of inflammatory factors in the muscle that can stimulate the surrounding nerves and cause the patient to experience pain. In the event of damage to the meniscus, cartilage, synovium and other tissues within the knee joint, the patient can pull and stimulate the damaged lesion during flexion, and the patient will also experience pain, interlocking, and impingement, affecting knee flexion and extension activities. When the patient has pain in the knee when the leg is bent, the patient needs to rest in bed. In the knee joint area, you can apply topical Tongluo pain relief cream or inject sodium glass acid into the joint, which can play a role in nourishing the cartilage and synovial membrane, and also can make the patient’s pain level reduced.