Temporomandibular joint (TMJ) syndrome or TMJ joint disorders are medical problems related to the jaw joint. The TMJ connects the lower jaw to the skull (temporal bone) under your ear. Certain facial muscles control chewing. Problems in this area can cause head and neck pain, a jaw that is locked in position or difficult to open, problems biting, and popping sounds when you bite.

The TMJ is comprised of muscles, blood supplies, nerves, and bones. You have 2 TMJs, one on each side of your jaw.

Muscles involved in chewing (mastication) also open and close the mouth. The jawbone itself, controlled by the TMJ, has 2 movements: rotation or hinge action, which is opening and closing of the mouth, and gliding action, a movement that allows the mouth to open wider. The coordination of this action also allows you to talk, chew, and yawn.

If you place your fingers just in front of your ears and open your mouth, you can feel the joint and its movement. When you open your mouth, the rounded ends of the lower jaw (condyles) glide along the joint socket of the temporal bone. The condyles slide back to their original position when you close your mouth. To keep this motion smooth, a soft disc lies between the condyle and the temporal bone. This disc absorbs shock to the temporomandibular joint from chewing and other movements. Chewing creates a strong force. This disc distributes the forces of chewing throughout the joint space.