An alternative explanation for the genesis of closed-lock symptoms in the internal derangement process.

Clinical and surgical data on 194 operated joints (135 patients) were used to substantiate a new concept challenging the presumed natural history of temporomandibular internal derangement (ID). A number of findings were incompatible with the traditional depiction of a progressive process based on gradual changes in disc position and shape. These findings were a lack or correlation between increasing age and the stages of the process; the percentage of patients in the third stage (closed lock) with limited opening (less than 25 mm) too severe to be caused solely by a nonreducible, displaced disc; the unexpectedly high incidence (greater than 50%) of normally shaped discs in the third stage of the process. A specific condition of severe and stubborn limited maximal mouth opening caused by total cessation of gliding, liable to occur at any age and unrelated to disc shape or position, which responds successfully to simple treatment by lavage and lysis, pressured injection, or arthrocentesis, was discerned. Lack of gliding was attributed to adherence of the disc to the fossa by a reversible effect such as a vacuum and/or decreased volume of synovial fluid of high viscosity. This condition was deemed worthy of an independent identity, dissociated from disc displacement, as a causative factor in the second and third stages of ID, and particularly as an aid to accurate diagnosis and treatment.