"Stands for temporomandibular joint, which is the hinge joint that connects the lower jaw (mandible) to the temporal bone of the skull, which is immediately in front of the ear on each side of your head."* (*Taken from WebMD.) Disorders can occur with this joint and the surrounding facial muscles that control chewing and the movements of your jaw.
MPD, myofacial pain dysfunction, is the most common condition causing patients to complain about TMJ, and it usually is a spasm of the muscles which control jaw position. Treatment of this muscle spasm can relieve symptoms. This usually is a lasting solution.