Anatomy of the Temporomandibular Joint

The mandibular condyle is centered on the glenoid fossa when the mouth is closed. When the mouth is open, the condyle moves anteriorly under the center of the articular eminence.

The disc has anterior (A) and posterior (P) bands. The thinner central portion is called the intermediate zone (iz). The posterior band is normally located directly on top of the condyle (C) when the mouth is closed. The intermediate zone should be between the condyle and the closest portion of the temporal bone in any mouth position. The disc is low signal on all MR sequences, but you may be able to see intermediate signal centrally in the anterior and posterior bands.

The posterior aspect of the disc attaches to the bilaminar zone, collagen fibers that pull the disc back when it moves forward.

Reference

Helms CA, et al. Musculoskeletal MRI. Second edition. pp 172-173.