Temporomandibular Joint (TMJ) anatomy
The temporomandibular joint (TMJ) makes possible the various movements of the mandible. It allows for the up, down, forward, backward, and side to side movements. All movements of the mandible and the functioning of the teeth are closely associated with the TMJ. The structures of the TMJ and some information about how they function follow.
Bones. The temporomandibular joint derives its name from the two bones that form the joint, the temporal bone and the mandible. The condyloid process of the mandible and the mandibular fossa of the temporal bone form the joint. The condyle moves (articulates) inside the fossa and makes the movements of the mandible possible. It provides for –
- Up and down movements (elevation and depression),
- Forward and backward movements (protrusive and retrusive),
- Side-to-side movements(lateral and rotational).
Articular Disc. The articular disc is a thin, biconcave, oval plate made of fibrous tissue, located between the mandibular fossa and the condyle of the mandible and the articular tubercle (posterior tubercle) of the temporal bone. The disc divides the TMJ into upper and lower cavities, each having synovial membranes which secrete synovial fluid to lubricate the joint. The edges of the disc are attached to the capsular ligament and, in front, it is attached to the lateral pterygoid muscle.
Ligaments. A ligament is a tough, fibrous band that connects bones. There are four ligaments that limit the extreme movement of the mandible. These are the-
- Capsular ligament,
- The lateral (temporomandibular) ligament,
- The sphenomandibular ligament,
- The stylomandibular ligament.