Pain in the tendons behind the knee joint is commonly caused by degenerative osteoarthritis of the knee joint and muscle and tendon injuries behind the knee joint. If the pain is from top to bottom, there is a possibility of lumbar disc herniation, as follows: First, degenerative osteoarthritis of the knee joint: degenerative osteoarthritis of the knee joint in patients can be followed by joint effusion, which can lead to the formation of popliteal cysts, which are increasing in size and can compress the blood vessels in the popliteal fossa nerves and tendons, thus causing painful symptoms in the tendons behind the knee joint with limited knee movement and swelling of the knee joint, the diagnosis can be established by MRI. Second, muscle and tendon injuries behind the knee: most of the muscle and tendon injuries behind the knee occur during strenuous exercise, the patient will have local pain symptoms after the tendon injury, and accompanied by limited movement of the knee and lower leg, unable to stand and exercise for a long time. Therefore, patients with tendon pain behind the knee should be diagnosed and treated early, and the symptoms can be significantly relieved by treating the primary disease of the joint. If it is caused by trauma, cold compresses and braking are required.