Magnetic resonance imaging of temporomandibular joint synovial fluid collection and disk morphology

Objective. The purpose of this study was to determine the features of synovial fluid, the shape of the disk, and the presence of disk displacement without reduction (DDsR) of the temporomandibular joint. Study design. A total of 612 bilateral temporomandibular magnetic resonance images of 306 patients were reviewed. The status of the joint was categorized as follows: normal disk position, disk displacement with reduction, acute DDsR, subacute DDsR, and chronic DDsR. The disk shape was characterized as one of following: biconcave, capshaped, cup-shaped, flattened, eyeglass-shaped, amorphous, or discontinuous. The amount of synovial fluid was divided into 4 categories: not observed, small, moderate, or large. Results. Synovial fluid collection was observed more frequently with subacute DDsR and when the disk was a folded shape. Conclusion. Synovial fluid collection, which was observed on T2-weighted magnetic resonance images, is more frequent in the early stage of DDsR. In addition, high signal intensity within the disk space should be considered a simple matter of fluid collection.