The preoperative examination findings in the soft tissue and bone of 22 temporomandibular joints of 15 patients with rheumatic disease were compared with the diagnosis after TMJ surgery. Agreement was found in 15 joints with rheumatic involvement and in 4 with internal derangement. In 5 (with unsuccessful arthrotomography) of the 15 rheumatic joints, magnetic resonance imaging showed destruction of disks with soft-tissue replacement, corresponding to fibrous tissue/ankylosis observed at surgery. Bony fusions in 2 of these joints were depicted with computed tomography. In the remaining 10 joints, arthrotomography showed irregularly outlined small compartments corresponding to synovial proliferations observed during surgery. Similar arthrotomographic interpretation, however, was made in 2 of 3 temporomandibular joints with imaging-surgery disagreement; surgery showed fibrous adhesions. In the third joint with unsuccessful arthrotomography, magnetic resonance imaging showed internal derangement but no synovial proliferations that were surgically observed. As experienced with other joints, synovial proliferations (or fibrous adhesions) could not be depicted with magnetic resonance imaging. Thus, differentiation between internal derangement with and without rheumatic involvement could be impossible with both arthrotomography and unenhanced magnetic resonance imaging.