The temporomandibular joint, or TMJ, works like a hinge for your jaw. TMJ disorders can cause pain in the jaw joint and the muscles that control the jaw, pain around the ear, difficulty chewing, or facial ache. Also, TMJ can cause a clicking sound upon opening the mouth. TMJ may be caused by genetics, arthritis, injury, or a combination of factors. Grinding your teeth, which is called bruxism, sometimes is associated with jaw pain, but many people clench their teeth without developing TMJ. The pain and discomfort of TMJ disorders usually is temporary. Symptoms usually come on gradually with no precipitating injury or event.