Thirty-five patients with internal derangement of the temporomandibular joint who had unilateral anterior disc displacement without reduction were studied. The patients were classified according to the degree of disc displacement and the presence or absence of an abnormal disc configuration on magnetic resonance imaging (MRI). Arthroscopic examination of the upper joint compartment was also performed, and intra-articular changes on the disc surface, the articular surface of the temporal bone (load-bearing areas) and the synovial lining (a load-free area) were classified. The findings were compared with the corresponding mandibular tracking patterns to study the association between these factors. The results were as follows:
1. There was no discernible relation between the mandibular tracking patterns and the disc conditions (degree of disc displacement and disc configuration on MRI).
2. An analysis of the arthroscopic findings of the upper joint compartment and the corresponding mandibular tracking patterns revealed no distinct relation between the mandibular tracking patterns and morbid findings of the articular surface of the temporal bone and disc surface. However, there was a significantly increased incidence of decreased range of opening motion (p<0.05) and unstable maximum opening position (p<0.01) among patients with evidence of fibrous adhesion of the synovial wall, especially at the anterolateral portion of the upper joint compartment, and those with fibrosis of the synovial wall.