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Topic

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Articular capsule of temporomandibular joint

The articular capsule of the temporomandibular joint (TMJ) is a fibrous structure that envelops and stabilizes the TMJ, providing support and limiting excessive movements. It is integral to joint function, protecting the articular surfaces and facilitating smooth articulation between the mandibular condyle and the temporal bone. Understanding its anatomy and imaging characteristics is essential in diagnosing TMJ disorders and pathologies.

Synonyms

  • TMJ capsule

  • Capsular ligament of TMJ

  • Capsula articularis articulationis temporomandibularis (Latin)

  • Fibrous capsule of TMJ

Anatomical Description

  • The articular capsule is a thin, fibrous membrane enclosing the TMJ.

  • Superior attachment: Margins of the mandibular fossa and articular tubercle of the temporal bone.

  • Inferior attachment: Surrounds the neck of the mandibular condyle.

  • Composed of dense connective tissue with both superficial and deep layers.

  • Lined internally by the synovial membrane.

  • Reinforced laterally by the lateral (temporomandibular) ligament.

  • Looser posteriorly and medially, allowing mandibular movement.

  • Functions to contain synovial fluid, support the joint, and limit excessive motion.

MRI Appearance

Proton Density (PD) Sequence

  • The articular capsule appears as a thin, low-signal-intensity linear structure outlining the TMJ.

  • Seen best in oblique sagittal or coronal planes along the long axis of the condyle.

  • Adjacent structures such as the disc and synovial fluid provide contrast for better delineation.

  • Effusion or capsular thickening appears as increased signal or bulging adjacent to the normal capsule line.

Short Tau Inversion Recovery (STIR) Sequence

  • The capsule itself remains low signal (hypointense) on STIR due to its fibrous composition.

  • Increased fluid within the capsule or synovial inflammation is highlighted as high signal intensity (bright) adjacent to or surrounding the capsule.

  • Useful for detecting capsulitis, effusion, or peri-capsular edema.

  • Helps differentiate between normal capsule, joint fluid, and pathologic changes.

MRI images

Articular capsule of temporomandibular joint