A patient has clicking on opening, and the panoramic radiograph shows a condyle that appears eroded and reduced in size. What is the most likely diagnosis?

Correct answer: C. Rheumatoid arthritis

• A. An osteochondroma appears as a bony outgrowth adding mass to the condyle, not as erosion reducing it.
• B. Synovial chondromatosis shows multiple loose calcified bodies within the joint space, a distinctive and quite different appearance.
• C. CORRECT. RHEUMATOID ARTHRITIS attacks the TMJ in roughly half of patients with the disease. The inflamed synovial pannus erodes the condylar head, producing the characteristic radiographic picture of a small, flattened, eroded condyle — sometimes described as 'sharpened pencil'. Progressive condylar resorption shortens the ramus, and bilateral involvement causes an ANTERIOR OPEN BITE with a retruded chin.
• D. Condylar hyperplasia produces an ENLARGED condyle with facial asymmetry and a deviated chin — the opposite radiographic finding.

Note: Distinguish it from OSTEOARTHRITIS, which is degenerative rather than inflammatory, usually unilateral, and shows flattening, osteophytes, subchondral sclerosis and Ely cysts — bone being ADDED at the margins as well as lost. RA is inflammatory, typically bilateral and symmetric, erosive without osteophyte formation, and accompanied by involvement of the small joints of the hands and by morning stiffness.