Temporomandibular joints — TMJs — are located on both sides of the face in front of the ears, connecting the jawbone (mandible) to the skull (temporal bone). They're the most complicated joints in the human body, providing rotation (pivoting) movement like all joints, as well as sliding movement, called translation. That's what allows us to open our mouths wide and move our jaws from left to right. Between the top end of the jaw (condyle) and the socket in the skull is a disc of cartilage, which — like the discs in the neck and back — serve as shock absorbers, protecting the bones from hitting each other.

The joints work with the neuromuscular system
The movement of the jaw is orchestrated by a complex set of muscles, which are, in turn, controlled by the body's local and central nervous system. Together, they're called the neuromuscular system. The whole jaw-joint system is held together by ligaments, which limit the range of motion in all directions — as they do in all the joints of the body.

A unique system of many parts
The TMJ joint system is unique in many ways. The left and right joints must coordinate, working at the same time for the jaw to move. While the opening, lateral and forward movements of the jaw are controlled by the shape of the bones and are a function of muscles and ligaments, the closing end-point of the jaw movement is controlled by the coming together of the teeth — the bite or occlusion. No other joint in the body has such a rigid end-point limit.

The proper, healthy function of the TMJ system requires normal structure and function of all the component parts, including muscles, nervous system, ligaments, joints (bones, discs and connecting tissues) and the dental occlusion.