Degenerative temporomandibular joint disease in a lioness (Panthera leo)

The temporomandibular joint (TMJ) is a synovial joint that consists of two articulating surfaces, the mandibular head on the condylar process ventrally and the mandibular fossa of the squamous temporal bone dorsally, with a thin fibrocartilage disc that separates the joint into two non-communicating compartments. Degenerative joint disease (DJD) of the TMJ has been evaluated in other carnivorous species; however, it has not previously been described in the lion (Panthera leo). This study characterized the histological, biomechanical and biochemical properties of the TMJ in health and disease in a lioness. The components of the articulating surface and general features of the disc of the TMJ were comparable to other carnivorous species described previously. Spontaneous DJD was observed unilaterally, revealing comparable features with other carnivores. Tensile strength and stiffness differed substantially between the diseased and healthy disc, with the diseased disc having altered direction-dependent mechanical properties. Biochemically, the disc exhibited a similar pattern of collagen and glycosaminoglycan composition to other carnivores. The role of DJD of the TMJ in potential pain or disability is not well understood in these species, and this report offers a glimpse into these disorders.