Knee pain may be caused by meniscus injury, arthritis, synovitis and ligament injury. 1. Meniscus injury: meniscus injury is the integrity and continuity of the meniscus has been damaged, the cause of the disease and sprains, violent trauma, long-term fatigue and other factors. Patients will have leg joint pain, pain, swelling and other symptoms. 2. Arthritis: Arthritis includes osteoarthritis, rheumatoid arthritis and gouty arthritis. Osteoarthritis is a chronic disease that progresses gradually and is mostly related to factors such as heredity, infection, joint damage and metabolic disorders. Rheumatoid arthritis is arthritis caused by immune diseases. Gouty arthritis is caused by abnormal purine metabolism. Patients will have knee pain, swelling and other symptoms. 3. Synovitis: Synovitis is an inflammatory change in the synovium caused by bacteria or Mycobacterium tuberculosis, and the cause of the disease is mostly related to excessive joint movement, infection and other factors. Patients will have symptoms such as pain in leg joints and limitation of joint movement. 4. Ligament injuries: including lateral collateral ligament and cruciate ligament injuries, can be due to ligament injuries appear ligament pain, manifested as knee joint pain. There are many causes of leg joint pain, and there may also be fracture, dislocation, bone tumor and popliteal cyst, etc. It is recommended that the patient should seek medical treatment in time, and under the guidance of the doctor to carry out relevant examinations and standardized treatment. Patients need to take more bed rest in daily life to avoid excessive activities causing joint involvement.