Temporomandibular joint and muscle disorders, commonly called "TMJ," are a group of conditions that cause pain and dysfunction in the jaw joint and muscles that control jaw movement. Some estimates suggest that TMJ disorders affect over 10 million Americans; the conditions appear to be more common in women than men.

Trauma to the jaw or temporomandibular joint plays a role in some TMJ disorders but in most cases, the exact cause of the condition is not clear. A variety of symptoms may be linked to TMJ disorders. Pain in the chewing muscles and/or jaw joint is the most common symptom; others include jaw muscle stiffness; limited movement or locking of the jaw; painful clicking, popping or grating in the jaw joint when opening or closing the mouth; and a change in the way the upper and lower teeth fit together.