Characterization of degenerative changes in the temporomandibular joint of the bengal tiger (Panthera tigris tigris) and siberian tiger (Panthera tigris altaica).

The articulation of the temporomandibular joint (TMJ) is composed of the temporal bone dorsally, the mandibular condyle ventrally and a fibrous articular disc. The TMJ disc plays an essential role in distributing load between the two articular surfaces. Degeneration of the disc in the presence of joint pathology has been shown in man; however, TMJ pathology has not been documented previously in tigers (Panthera tigris). The mandibular condyle and TMJ disc of a Bengal tiger (P. tigris tigris) and a Siberian tiger (P. tigris altaica) were evaluated grossly and the TMJ disc was characterized biochemically and mechanically. Characterization of the TMJ disc verified region- and direction-dependent biochemical and mechanical properties, reflective of the functional demands on the joint. Degenerative joint disease was observed in both cases and this was more severe in the Siberian tiger. Simultaneous evaluation of joint pathology, biochemical composition and mechanical properties of the TMJ disc revealed a loss in functional properties (tensile anisotropy) of the disc as joint pathology advanced from moderate to severe. TMJ degeneration may compromise the ability of the animal to eat and thrive and may be a factor contributing to the endangered status of these species.