Learning Objective: By the end of this session, the learner will be able to describe the anatomy, articulating surfaces, ligaments, movements, neurovascular supply, and clinical relevance of the temporomandibular joint (TMJ).
The temporomandibular joint is formed by the articulation of the mandible and the temporal bone, located just anterior to the tragus on the lateral face. It is a unique synovial joint with complex movement patterns required for chewing, speaking, and maintaining oral function.
Articulating Surfaces
The TMJ consists of articulations between:
- Mandibular fossa (temporal bone)
- Articular tubercle (temporal bone)
- Head of the mandible
A key feature of this joint is the articular disk, which prevents direct contact between bony surfaces. The disk divides the joint into two synovial cavities, each lined with synovial membrane. Unlike most synovial joints, the articular surfaces are covered by fibrocartilage, not hyaline cartilage.
Ligaments
Three extracapsular ligaments stabilize the TMJ:
- Lateral ligament – thickening of the capsule; prevents posterior dislocation.
- Sphenomandibular ligament – extends from the sphenoid spine to the mandible.
- Stylomandibular ligament – thickened parotid fascia; supports mandibular weight with facial muscles.
Movements of the TMJ
TMJ movement is produced by the muscles of mastication and hyoid muscles, with each joint compartment having distinct roles:
Upper Joint (Gliding Movements)
- Protrusion – lateral pterygoid (assisted by medial pterygoid).
- Retraction – posterior temporalis fibers.
- Lateral (side-to-side) chewing motion – alternating protrusion/retraction.
Lower Joint (Hinge Movements)
- Depression (opening) – mostly gravity; assisted by digastric, geniohyoid, mylohyoid when resisted.
- Elevation (closing) – powerful movement performed by the temporalis, masseter, and medial pterygoid.
Neurovascular Supply
-
Arterial supply: branches of the external carotid artery, mainly the superficial temporal artery; others include deep auricular, maxillary, and ascending pharyngeal branches.
-
Innervation: auriculotemporal and masseteric branches of the mandibular nerve (CN V3).
Clinical Relevance
TMJ Dislocation
Anterior dislocation occurs when the mandibular head moves beyond the articular tubercle, often due to:
- Yawning
- Wide mouth opening
- Blow to the jaw
Patients cannot close their mouths, and nearby auriculotemporal and facial nerves may be injured in high-energy trauma. Posterior dislocation is rare due to the strength of the lateral ligament and the postglenoid tubercle.
