Consider joint adhesion, osteoarthritis, joint infection, rheumatoid arthritis. 1. Joint adhesion: because of the lower limb surgery after a long period of bed rest, no rehabilitation exercise caused by the joint adhesion, joint stiffness, activity is limited, through the manipulation of relaxation or hot compresses, wax therapy and other methods can reduce. 2. Osteoarthritis: the elderly joint hyperplasia and degeneration, articular cartilage wear and tear, joint space significantly narrowing can cause knee stiffness, degeneration, joint flexion and extension activities are limited, can be improved by intra-articular injection of sodium hyaluronate or joint replacement. 3. Joint infection: Bacterial or tuberculosis infection of the knee joint causes joint effusion, joint adhesion causing stiffness, redness, swelling and heat pain of the joint, which may be relieved through anti-infection treatment. 4. Rheumatoid arthritis: synovitis destroys the joints, and inflammatory exudation, absorption and mechanization cause joint ankylosis, which is manifested as stiffness of the joints, and stiffness of the knee joints when the knee joints are involved. Symptoms can be relieved by the use of immunosuppressive drugs such as methotrexate and leflunomide. It is recommended to go to the hospital in time to clarify the cause of knee stiffness and treat the symptoms under the doctor’s guidance, do not self-medication.