Temporomandibular joint disorder (TMJ): A disorder of the temporomandibular joint(s) that causes pain, usually in front of the ear(s), sometimes in the form of a headache.
Pain in the TMJ can be due to trauma, such as a blow to the face; inflammatory or degenerative arthritis, or poor dental work or structural defects that push the mandible back towards the ears whenever the patient chews or swallows. Grinding or clenching the teeth due to stress is a frequent culprit. Sometimes muscles around the TMJ used for chewing can go into spasm, causing head and neck pain, and difficulty opening the mouth normally.
Treatment depends on the cause and severity of the problem, and can range from a mouth guard or medication to prevent nighttime tooth-grinding, to surgery.