Temporomandibular joint: from anatomy to internal derangement

Abstract

The temporomandibular joint can be affected by various conditions, such as joint dysfunction, degenerative changes, inflammatory processes, infections, tumors, and trauma. The aim of this pictorial essay is to help radiologists identify and describe the main findings on magnetic resonance imaging evaluation of the temporomandibular joint, given that the correct diagnosis is essential for the appropriate treatment of patients with temporomandibular joint disorders.

Keywords: Magnetic resonance imaging; Temporomandibular joint; Temporomandibular joint disorders; Temporomandibular joint dysfunction syndrome.

Figure 1

TMJ anatomy. Sagittal PD-weighted images and schematic drawings demonstrating the anatomy of the TMJ in closed-mouth and open-mouth positions (A and B, respectively). 1, mandibular condyle; 2, articular eminence of the temporal bone; 3, articular disc (anterior band); 4, articular disc (intermediate band); 5, articular disc (posterior band); 6, bilaminar zone; 7, superior and inferior bellies of the lateral pterygoid muscle.

Figure 2

Normal TMJ disc position. Sagittal and coronal PD-weighted images obtained in the closed-mouth position (A and B, respectively). Note that the junction of the posterior band of the articular disc and the bilaminar zone is near the 12 o’clock position or situated within 10° of that position (A). In the coronal plane (B), the articular disc (arrows) should not (and does not, in this normal image) extend beyond the medial or lateral edge of the condyle.

Figure 3

Condylar excursion. Sagittal PD-weighted images in the open-mouth position, showing excursion of the condyle. The dashed lines indicate the position of the articular eminence of the temporal bone. A: Appropriate excursion. Note that the mandibular condyle articulates with the temporal eminence in the open-mouth position. B: Decreased excursion. The condyle does not reach the plane of the temporal eminence in the open-mouth position. Note the degenerative changes, characterized by flattening of the condyle with irregularities of the articular surface, subchondral sclerosis, and an anterior osteophyte. In cases of increased excursion, the condyle passes beyond the temporal eminence in the open-mouth position.

Figure 4

Anterior disc displacement without recapture. Sagittal PD-weighted image in the closed-mouth position (A), showing the disc anterior to the 11 o’clock position. In the open-mouth position (B), there is no disc recapture. The disc position is indicated by the arrows.

Figure 5

Anteromedial disc displacement without recapture. Sagittal PD-weighted image in the closed-mouth position (A), showing anterior disc displacement. Coronal image (B) showing the disc in a medial location. In the PD-weighted sagittal acquisition in the open-mouth position (C), the condyle is not observed in the plane in which the disc is visualized, demonstrating that the disc remained in the medial location.

Figure 6

Posterior disc displacement with recapture. Sagittal PD-weighted images in the closed-mouth and open-mouth positions (A and B, respectively). Posterior displacement of the articular disc (yellow arrow) is accompanied by bilaminar thickening (red arrow) and joint effusion. Note the recapture of the articular disc (in B).

Figure 7

Degenerative disc changes. Sagittal PD-weighted image in the closed-mouth position, showing anterior disc displacement and morphological changes, with tapering and irregularities of the articular disc.

Figure 8

Disc perforation. Sagittal PD-weighted image showing discontinuity of the articular disc, with separation of the anterior band (yellow arrow) and posterior band (blue arrow). Note also the subcortical sclerosis with an anterior marginal osteophyte in the mandibular condyle.

Figure 9

Joint effusion. Sagittal T2-weighted image with fat saturation, showing joint effusion. Note the communication between the upper and lower joint cavities, indicating disc perforation.

Figure 10

Disc adhesion. PD-weighted sagittal images in the closed-mouth and open-mouth positions (A and B, respectively), showing alteration of the signal in the posterior band and intermediate zone of the articular disc, together with thickening of the retrodiscal tissue (yellow arrow). Note that the disc remains in the same location in the closed-mouth and open-mouth positions, which is characteristic of disc adhesion (stuck disc). Note also the thickening at the insertion of the lateral pterygoid muscle belly (red arrow), forming the double-disc sign.

Figure 11

Synovitis. Axial T2-weighted image with fat saturation (A) and contrast-enhanced T1-weighted image (B), showing synovial thickening with enhancement consistent with synovitis, which should not be confused with joint effusion.