Articular disk

Abstract: Temporomandibular joint (TMJ) dysfunction is a common condition that is best evaluated with magnetic resonance (MR) imaging. The first step in MR imaging of the TMJ is to evaluate the articular disk, or meniscus, in terms of its morphologic features and its location relative to the condyle in both closed- and open-mouth positions. Disk location is of prime importance because the presence of a displaced disk is a critical sign of TMJ dysfunction. However, disk displacement is also frequently seen in asymptomatic volunteers, so that other findings may be required to help make the diagnosis. These findings include thickening of an attachment of the lateral pterygoid muscle, rupture of retrodiskal layers, and joint effusion and can serve as indirect early signs of TMJ dysfunction. It is important for the radiologist to detect early MR imaging signs of dysfunction, thereby avoiding the evolution of this condition to its final stage, an advanced and irreversible phase that is characterized by osteoarthritic changes such as condylar flattening or osteophytes. Further studies conducted with the latest MR imaging techniques will allow a better understanding of the sources of TMJ pain and of any discrepancy between imaging findings and patient symptoms.

Abstract: The morphology, distribution, and function of mechanoreceptors in joint capsules, ligaments, knee-joint menisci, and articular disks of the temporomandibular joints of animals, including humans, have been reviewed. In addition to free nerve endings, three types of joint receptors are present in most animal joints: 1) a Ruffini-like receptor situated in the capsule, 2) a Golgi tendon organ situated in a ligament; and 3) the encapsulated Pacinian-like corpuscle. In the anterior cruciate ligament, nerve fibers enter from the subsynovial connective tissue and terminate in receptors. Most of the receptors are found in the distal portion of the ligament. In the meniscus, nerves penetrate the outer and middle one-third of the body and the horns from the perimeniscal tissue, with a greater concentration at the horns. In the temporomandibular articular disk, the mechanoreceptor density is greatest at the periphery and progressively decreases toward the center. If a joint has an intra-articular structure, mechanoreceptors undoubtedly are present within it. The concentration of mechanoreceptors appears greater in areas related to the extremes of movement and probably represents the first line of defense in sensing these extremes. These afferent discharges elicit support from discharging mechanoreceptors located in the joint capsule and subsequently from those in the surrounding muscles. This total afferent output alerts the central nervous system of impending injury, which can then be averted through reflex mechanisms.

Abstract: Out of 115 right temporomandibular joints from Swedish subjects aged 1 day to 93 years, 48 joints without any gross sign of arthrosis or deviation in form were examined histologically.The joint components were cut sagittaly, each into four parts. Histological sections were made of the condyle, the temporal component and of the articular disk. The total thickness of the soft tissue layers was measured in decalcified sections, cut from the medio-central and lateral parts of the condyle and the temporal component and from the medial, medio-central, latero-central and lateral regions of the disk. In the medio-central sections from the condyle and temporal component the thickness of the fibrous connective tissue layer i.e. the surface layer was also registered. The soft tissue layers were thickest in the condyle superiorly, about 0.4–0.5 mm, in the temporal component on the postero-inferior slope of the articular tubercle, about 0.5 mm, and in the disk posteriorly about 2.9 mm. In the roof of the fossa it was ...