Pain in the jaw joint when opening the mouth is mainly caused by uneven force on the temporomandibular joints bilaterally. This action is mainly in the usual chewing without bilateral force, habitual use of one side of the force. Habitual exertion on one side, the same side of the temporomandibular joint excessive force, so that the inside of the synovial membrane hyperplasia, cartilage wear and tear serious, the formation of temporomandibular arthritis. The opposite side is relatively mild, which causes bilateral TMJ activities not in the same horizontal axis. When chewing, the relative displacement occurs, resulting in increased pain on one side and no symptoms on the other. Once you know this principle, you need to change your chewing habit by chewing bilaterally to reduce or even eliminate the symptoms.