Anatomical Structures of the Temporomandibular Joint
The temporomandibular joint is a bilateral synovial articulation composed of five essential structures: the mandibular condyle, the mandibular (glenoid) fossa of the temporal bone, the articular disc, the joint capsule, and supporting ligaments. 1, 2
Bony Components
The TMJ forms a bicondylar articulation between the mandible and skull base, creating what is more accurately termed the craniomandibular articulation since both joints function as a mechanically integrated unit. 1
- Mandibular condyle: The condylar process of the mandible serves as the inferior articulating surface 3
- Temporal bone components: The mandibular (glenoid) fossa and articular eminence (joint tubercle) form the superior articulating surfaces 2, 3
- Articular surface composition: Unlike most synovial joints, the TMJ articular surfaces are lined with fibrocartilage rather than hyaline cartilage 2
Articular Disc
The articular disc is the critical structure that divides the TMJ into superior and inferior compartments, each allowing distinct types of movement. 2
- Disc structure: The disc has a thick peripheral rim with special viscoelastic properties that stabilize it between the condyle and articular eminence 4
- Disc function: It compensates for the lack of congruence between articular surfaces and has an extremely low coefficient of friction 4
- Compartmentalization: The disc creates two distinct joint spaces—the inferior compartment allows hinge movement, while the superior compartment permits translation or gliding motion 2
- Clinical significance: Disc displacement is among the most frequently found TMJ disorders and can occur in anterior, lateral, or medial directions 5
Soft Tissue Structures
- Joint capsule: A fibrous capsule encloses the joint and has privileged anterior relationships with the lateral pterygoid muscle 4
- Synovial membrane: The synovium nourishes and lubricates the avascular articular surfaces and possesses bactericidal properties 4
- Synovial fluid: Present within the joint spaces to facilitate smooth articulation 1
Supporting Ligaments and Muscles
- Ligamentous support: Tough adjacent ligaments provide joint stability 1
- Lateral pterygoid muscle: This muscle has two heads showing functionally reciprocal activation, with the superior head's exact insertion and role remaining controversial 4
- Disc attachments: Special disc attachments contribute to biomechanical stabilization through viscoelastic deformation mechanisms 4
Functional Anatomy
The TMJ is unique among joints because its movement is controlled not only by joint morphology but also by the dentition at the opposite end of the lever system. 4 Throughout life, the temporal, condylar, and discal articular surfaces undergo continuous remodeling in response to biochemical stimuli. 4
Clinical pitfall: The preservation and reattachment of the TMJ disc and lateral pterygoid muscle within the glenoid fossa is critical during any reconstructive procedures, as this sustains normal TMJ functionality and diminishes the likelihood of complications such as re-ankylosis. 5