The temporomandibular joints in adults. Old and new anatomical knowledge

The temporomandibular joints are the most moved joints in the human body and the third most frequent location of orofacial pain. Good anatomical knowledge about these structures is therefore essential. Phylogenetically, this squamosal- dentary joint is the most important characteristic of the mammalian skeleton. The articulating surfaces are formed by the mandibular condyle and the dorsal and crestal parts of the articular eminence. Avascular articular cartilage covered with a connective tissue layer covers the bone. The articular disc, which is suspended like a hammock from the base of the skull, shows a wide variety of shapes that can differ from the typical biconcave-biconvex textbook illustrations. The disc is a mobile and shape-changing socket for the condyloid process. It serves as a shock absorber and distributor of forces under compressive, tensile, and shearing loads. The articular disc and the loose articular capsule form a functional unit: the discocapsular system. The double-layered synovial membrane that covers the articular capsule towards the articular cavity produces, secretes, and absorbs the synovial fluid. It is responsible for supplying nutrients and for the metabolism of the articular cartilage and the disc. Keywords: articular disc, phylogeny, synovial membrane, temporomandibular joints (TMJs), TMJ capsule