Anchored disc phenomenon with a normally positioned disc in the temporomandibular joint: characteristics and behaviour.

We aimed to elucidate the pathogenesis and evaluate the therapeutic behaviour of patients with an anchored disc phenomenon but a normally positioned disc of the temporomandibular joint (TMJ). Fourteen patients with internal derangement including closed lock of one TMJ were examined. All had normally positioned discs. Synovial fluid was collected from the TMJ by arthrocentesis. Their symptoms, and the protein concentration in the synovial fluid, were evaluated. Their median duration of illness was 3 months (range 0.5-12), and the median protein concentration was low (343 microg/ml; range 36-791). Arthrocentesis was successful in nine. Arthroscopic findings in the five unsuccessful cases showed severe intra-articular adhesions of the TMJ. The main intra-articular pathological feature was the presence of adhesions, which might be affected by low protein concentrations in the synovial fluid. These findings may provide a new treatment in patients with normally positioned discs, despite the small number studied.