After middle age, the muscles and ligaments of the knee joint begin to undergo degenerative changes, the synovial fluid secretion in the joint cavity decreases, the bone surface of the joint rubs together for a long time to form bone wear, and the tissues around the joint are prone to fibrous adhesions due to inflammation, so the elderly often feel the stiffness of the knee joint, and the activity will make a “click” sound or friction sound. This can lead to pain, swelling, and joint effusion when exposed to cold or excessive activity, and in severe cases, joint deformity and disability. Specifically, the causes of knee pain in the elderly are as follows: 1. Chronic synovitis: chronic pain and swelling in the knee joint. Synovial effusion and synovial hypertrophy can be seen on physical examination. 2. Patellar deviation: the knee joint is sore and weak after activity, improves after rest, and is painful when semi-squatting. 3, free body in the knee joint: the patient’s leg is weak or has a feeling of joint jamming, and there is a friction sound under the patella. 4, prepatellar bursitis: there is a history of trauma, causing prepatellar pain, and localized pressure pain on physical examination. 5, osteoarthrosis: joint pain is obvious after sitting or squatting for a long time, when standing up or going up or down stairs, and relieved after rest. 6, pseudogout: more male patients, preferably in the knee joint. X-rays show calcification of meniscus and articular cartilage surface. 7, femoral head necrosis: hip lesions with knee pain symptoms. 8, soft tissue injury around the knee joint: the knee joint has many muscles wrapped around it, due to soft tissue injury around the knee joint can also cause knee pain. Like semitendinosus, semimembranosus, gastrocnemius, hallux valgus muscle injury and so on.