Swan neck deformity presents with which pattern of joint movement and is commonly associated with rheumatoid arthritis?

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

Answer: (B)

Swan neck deformity presents with proximal interphalangeal joint hyperextension while the distal interphalangeal joint remains flexed. In rheumatoid arthritis, chronic joint inflammation weakens and stretches the volar plate and surrounding ligaments at the PIP, allowing the PIP to drift into hyperextension. This imbalance of the extensor mechanism means the DIP tends to stay flexed due to the pull of the flexor tendons, producing the distinctive posture. Other deformities involve different patterns—Boutonniere deformity shows PIP flexion with DIP extension, Mallet finger is DIP flexion from extensor tendon injury, and ulnar drift refers to MCP joints drifting ulnarly in RA.