In permanent temporomandibular disc displacement (TMJ-DD) outcome studies many authors claim positive effects of arthroscopic surgery, arthrocentesis and physical therapy. This literature review was undertaken to analyse whether the claimed effects are based on acceptable methodology. The recorded papers were analysed by two independent observers according to (1) method of investigation, (2) therapeutic intervention studied, (3) therapeutic outcome variables used, and (4) claimed effectiveness of the intervention. Agreement between observers was calculated. Twenty-four papers were found in which therapeutic outcome of interventions on temporomandibular disorders were studied. Six studies applied a true experimental design. Each of these six studies compared a different set of interventions. Twenty-two papers used maximal mouth opening (MMO) as an outcome variable, nine studied pain intensity on a visual analogue scale, one paper assessed the mandibular function impairment questionnaire. Kappa for overall agreement concerning the reviewing criteria was 0.82 (P < or = 0.001). No distinguishing effects on MMO, pain or function impairment were reported between arthroscopic surgery, arthrocentesis and physical therapy. Results of methodological sound outcome studies evaluating the effects of arthroscopic surgery, arthrocentesis and physical therapy are needed.