The Temporomandibular Joint

The temporomandibular joint is split into two sections by an articular disc (or meniscus), a fibrocartilagenous structure that enables a greater range of movement of the joint.

Temporomandibular dislocations may be unilateral or bilateral and occur in anterior, posterior, lateral and superior positions. The anterior is by far the most common, the others all being associated with a fracture of either the mandible or base of the skull. Anterior dislocation may be traumatic or atraumatic; in trauma it is normally caused by direct downward force to a partially opened mouth.

In predisposed patients with shallow mandibular fossae or underdeveloped mandibular condyles, certain repeated activities may initially sublux, then dislocate, the mandible. The most common mechanism relates to excessive opening of the mouth when: yawning, laughing, shouting, eating and during dental work.

Connective tissue disorders, such as Marfan’s and Ehlers-Danlos syndrome, increase likelihood of dislocation. Once the mandible has dislocated anteriorly, spasm of the masseter and pterygoid muscles occurs which further traps the dislocated condyle.