1, masticatory muscle disorders: including myofascial pain, myositis, myospasm, degenerative contracture of muscle fibers and unclassified limited myalgia. 2, structural disorders: changes in the normal organic structural relationship of the joint, various joint disc displacements (reversible disc anterior displacement, irreversible disc anterior displacement, joint disc rotation displacement and joint disc internal and external displacement, etc.), joint capsule expansion and joint disc attachment relaxation or avulsion, etc. 3, joint inflammatory diseases: synovitis and/or arthritis of the joint capsule, which can be divided into acute and chronic. 4, osteoarthrosis: can be divided into primary osteoarthrosis and secondary osteoarthrosis, according to the disease process can be divided into I ~ IV four stages. This classification method is basically adapted to the current clinical and scientific research work of TMJ disorders in China, but many changes such as articular cartilage changes, synovial lesions, muscle blood supply, etc., which can only be detected by arthroscopy, isotope scan and infrared thermography, are not included; in addition, TMJ disorders caused by psychological factors are not included.