PURPOSE The purpose of this investigation was to determine the relationship between arthroscopically diagnosed synovitis and adhesions in a population of patients with significant limitation of mandibular opening and temporomandibular joint pain. PATIENTS AND METHODS Temporomandibular joint arthroscopy was performed on 126 joints in 80 patients (female:male = 5.7:1; mean age = 35.5 years; mean duration of symptoms = 50 months). All patients were diagnosed with severe temporomandibular joint disease recalcitrant to conservative therapy. Each joint was evaluated arthroscopically for the presence of synovitis and adhesions. Chi-squared analysis was performed to determine if there was a significant relationship between the presence of synovitis and adhesions. RESULTS Diagnostic arthroscopic examination showed the following: no synovitis and no adhesions in 18/126 joints (14%), no synovitis with adhesions present in 33/126 joints (26%), synovitis with no adhesions in 13/126 joints (10%), and synovitis and adhesions present in 62/126 joints (49%). Statistical analysis showed a significant relationship between arthroscopically diagnosed synovitis and adhesions. CONCLUSION Synovitis and adhesions are commonly present in the temporomandibular joints of patients requiring arthroscopic surgery due to painful limitation of mandibular movement. Excessive mechanical stress on the temporomandibular joint leads to maladaptive responses in the articular and synovial tissues, ultimately leading to synovitis, osteoarthritis and the formation of adhesions. An understanding of the pathogenic mechanisms that lead to synovitis, osteoarthritis and adhesions has important clinical implications for the nonsurgical as well as surgical management of patients suffering from these disorders.