Aetiology and management of the anterior dislocated disc. The anterior dislocated disc: some considerations of aetiology and clinical diagnosis.

The displacing temporomandibular joint disc presents an enigma. Modern imaging techniques of arthrography, CT, and MRI, as well as arthroscopy show that a displaced or even totally dislocated disc is not necessarily associated with disease, and such a joint can function quite without symptoms. Conversely these techniques, and notably arthroscopy, show that in some cases trauma initiates a cascade of events affecting not only the disc but also synovium, capsule, ligaments, and cartilage. Changes in synovial fluid, alterations in collagen, and associated release of pain-producing substances, cause alteration in joint dynamics. Reversible at early stages, these processes can produce adhesions which alter joint movement, including disc displacement. There is no single cause of disc displacement, but rather the effect of trauma on the interplay between structural, behavioural, and orthopaedic factors. Clinical diagnosis, excluding imaging, is briefly discussed emphasizing the concept of the barrier, and the use of diagnostic manipulation.