A 50-year-old woman with rheumatoid arthritis has radiographs of both hands showing periarticular osteopenia, symmetric joint space narrowing predominantly at the metacarpophalangeal and proximal interphalangeal joints, marginal erosions, and ulnar deviation of the fingers. Which additional radiographic finding, if present, would best distinguish this from osteoarthritis?
- A Osteophyte formation
- B Marginal erosions without osteophytes ✓
- C Subchondral sclerosis
- D Distal interphalangeal joint involvement
Correct answer: B. Marginal erosions without osteophytes
Explanation
In rheumatoid arthritis, inflammatory pannus erodes the bare areas of cartilage at joint margins, producing bare-area erosions without adjacent osteophytes or subchondral sclerosis. Osteoarthritis, by contrast, is characterized by joint space narrowing with subchondral sclerosis, subchondral cysts, and osteophytes reflecting a reparative process. Distal interphalangeal joint involvement and osteophytes are hallmarks of osteoarthritis and psoriatic arthritis, not rheumatoid arthritis.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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