\s=b\A retrospective analysis of 540 operated cases (740 joints) of internal derangements of the temporomandibular joint was carried out. Observations of this patient population provided the basis for describing pathological variations of internal derangements. Radiologic studies, including tomograms and arthrograms or magnetic resonance scans, and surgical/ pathological findings were correlated with clinical data in each case. It was found that clinical manifestations varied in a characteristic way and were directly related to the degree of pathological change and time course. Various stages of internal derangements were identified. Pathophysiological mechanisms responsible for the observed changes, as well as clinical signs and symptoms and causal factors, were discussed. Internal derangements are organic lesions that appear to be progressive and are probably of traumatic origin. The view is given that internal derangements represent the basic pathological entity responsible for clinical manifestations of what has been known as the temporomandibular joint pain-dysfunction syndrome or similarly described conditions. Effective clinical management takes on new importance because progression to advanced degenerative states may occur.

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One hundred painful temporomandibular joints in 100 patients were studied with highfield, surface-coil MR imaging. Partial flip angle or GRASS (gradient-recalled acquisition in steady state) and either T1-weighted or spin-echo long TR/short-long TE imaging techniques were used to assess the relative sensitivity and accuracy of these techniques in detecting joint fluid. lntraarticular fluid, interpreted to represent joint effusion, was observed in 88 of the 100 painful joints scanned. GRASS scans were obtained with the mouth closed, partially opened, and fully opened; T1-weighted and spin-echo images were obtained only with the mouth closed. Long TR/Iong TE spin-echo images were the most sensitive to fluid detection within the joint spaces. GRASS images were highly sensitive to intraarticular fluid, although the thicker scan section and local artifacts associated with these techniques resulted in lower accuracy compared with the spinecho long TR/Iong TE images. Joint fluid was directly observed in many of the 28 joints operated on from the series, and two of two joints were successfully aspirated. Osteochondritis dissecans and avascular necrosis are best demonstrated and staged with a combination of short TR/short TE and long TR/Iong TE weighted images, although a spin-echo long TR/short and long TE pulse sequence is more practical for this purpose. We recommend long TR/short and long TE spin-echo closed-mouth sagittal images combined with GRASS closed-and open-mouth views whenever inflammatory temporomandibular joint disease is suspected.

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