Background: The primary objective of this study was to assess the clinical effectiveness of fused images obtained from single-photon emission computed tomography (SPECT) and facial computed tomography (CT) for evaluat‑ ing degenerative changes in the mandibular condylar head. This assessment was accomplished by comparing the Technetium-99 m methylene diphosphonate ( 99m Tc-MDP) uptake ratio with the results of clinical and radiographic findings. Methods: The study included 17 patients (3 males and 14 females) with suspected osteoarthritis of the mandibular condyle, totaling 34 temporomandibular joints (TMJs). Based on clinical and radiographic examinations, the TMJs were categorized into four groups: normal (group N), internal derangement (group ID), osteoarthritis (group OA), and osteoarthritis sequelae (group ­OA seq ). For each patient, bone SPECT and facial CT scans were registered and reconstructed to create fused SPECT/CT images. The 99m Tc-MDP uptake levels in the TMJs were statistically com‑ pared among the four groups. Results: The 99m Tc-MDP uptake ratio showed a gradual increase in the order of the following: group N, group OA seq , group ID, and group OA. There was a significant difference observed among groups (pConclusion Fused SPECT/CT image can be an effective tool for evaluating degenerative changes in the mandibular condylar head. The technique demonstrated the ability to differentiate between normal TMJs and those with internal derangement, osteoarthritis, or osteoarthritis sequelae. This approach holds promise as a valuable method in clinical assessments of TMJ degeneration.