The Articular-Synovial Lining Tissue System in Temporomandibular Joints of Young Adults

The histologic character of the articular surfaces and synovial tissues in the temporomandibular joints of 20 young adults was described. Each joint compartment had a continuous connective-tissue lining that was fibrous on the articular surfaces, went through a transition, and was continuous with the lining tissue in the recesses. Areolar synovial tissue was found only in the upper posterior recess of the temporomandibular joint, fibrous synovial tissue was predominantly found in the upper anterior and lower posterior recesses, and an intermediate type of synovial tissue was found in the lower anterior recess. There was no distinct boundary between articular and synovial tissue. The structure and continuity of these lining tissues suggest that they constitute a continuous tissue system, here termed the "articular-synovial lining tissue system," that has a histologic character which depends on location and functional demands. It is hypothesized that all of the lining tissues should be considered synovial, based on a functional definition of nonadherence.