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Articular surface of mandibular fossa

The articular surface of the mandibular fossa is a smooth, concave region located on the temporal bone of the skull, forming a key component of the temporomandibular joint (TMJ). This surface articulates with the head (condyle) of the mandible, facilitating the hinge and sliding movements of the jaw. The articular surface is covered by fibrocartilage and separated from the condyle by an articular disc, playing a vital role in jaw mobility and function. Understanding its anatomy and MRI appearance is essential for diagnosing TMJ disorders and planning interventions.

Anatomical Description

  • The articular surface is located on the squamous part of the temporal bone.

  • Forms the superior part of the TMJ (temporomandibular joint).

  • Concave and smooth, covered by a thin layer of fibrocartilage (not hyaline cartilage).

  • Bordered anteriorly by the articular eminence and posteriorly by the tympanic part of the temporal bone.

  • Separated from the mandibular condyle by the intra-articular disc, which is also composed of fibrocartilage.

Synonyms

  • Glenoid fossa (mandibular fossa)

  • Temporal fossa (context-specific, but less accurate)

  • Fossa mandibularis (Latin term)

MRI Appearance

  • Proton Density (PD) Sequence:

    • The articular surface appears as a thin, low signal intensity line corresponding to the cortical bone.

    • The fibrocartilage covering is also low signal on PD, making differentiation from adjacent bone difficult unless there is pathology.

    • The adjacent marrow of the temporal bone shows intermediate signal due to fat content.

    • The articular disc (between the surface and condyle) appears as a thin, low signal structure.

  • STIR (Short Tau Inversion Recovery) Sequence:

    • The articular surface itself remains a low signal line (dark), similar to other cortical bone.

    • STIR is sensitive for fluid and edema; no signal increase is seen in the normal articular surface.

    • Pathological changes (e.g., bone marrow edema, inflammation) may appear as high signal intensity in the adjacent marrow or soft tissue, but the articular surface proper remains hypointense.

    • The articular disc maintains low signal unless affected by edema or degeneration.

MRI images

Articular surface of mandibular fossa