The present study aimed to clarify the reliabilities of four characteristic appearances, subchondral cyst, erosion, generalized sclerosis, and osteophyte, for evaluation of degenerative diseases with osseous changes in the temporomandibular joint (TMJ) using panoramic TMJ projection imaging and computed tomography (CT), and to investigate the imaging features of these modalities for subchondral cyst with reference to its magnetic resonance imaging (MRI) features.The reliabilities (κ values) of panoramic TMJ projection and CT images were determined by three radiologists for each characteristic appearance of TMJ osseous changes in 146 condyles. The features of cyst-like areas on CT images with agreement among the three radiologists were investigated for size, location, and continuity with the joint space together with MRI signal intensity and surrounding edema-like lesions.Panoramic TMJ projection images showed moderate and substantial agreements for erosion and osteophyte evaluations, respectively; while CT images showed substantial agreements for subchondral cyst, erosion, and osteophyte evaluations. Cyst-like areas on CT images were predominantly located in the central parts and 69 of 86 (80.2%) areas showed no communication with the joint space. Cyst-like areas with diameters exceeding 2 mm showed high or moderate MRI signal intensities. Edema-like lesions were observed in 10 of 28 (29.4%) condyles.The reliabilities of panoramic TMJ projection and CT images were clarified for each characteristic appearance. The results support the bone contusion theory for the formation of subchondral cysts in the TMJ. A possible improvement in reliability is suggested relative to MRI findings.
