Which finger deformity is commonly associated with rheumatoid arthritis?

• A. Boutonniere Deformity
• B. Swan Neck Deformity
• C. Ulnar Drift
• D. Z Deformity

Answer: (B)

Rheumatoid arthritis often damages the structures around the finger joints, and this inflammation disrupts the balance of the finger’s extensor mechanism. The result is a classic finger deformity where the proximal interphalangeal joint (PIP) bends into hyperextension while the distal interphalangeal joint (DIP) remains flexed or neutral. This pattern, known as swan neck deformity, reflects degeneration of the volar plates and misalignment of the extensor tendons, driven by chronic synovitis and ligament laxity. It’s one of the most characteristic finger deformities seen with RA because it directly mirrors the injurious changes in the finger’s soft tissues.

Boutonnière deformity involves flexion of the PIP with extension of the DIP due to central slip injury; ulnar drift is the sideways drift of fingers at the MCP joints toward the ulnar side; Z deformity refers to a thumb deformity involving the thumb’s MCP and IP joints. The question focuses on a finger deformity most commonly associated with RA, and swan neck is the best match.