Swan neck deformity is a characteristic hand deformity seen in rheumatoid arthritis, defined by hyperextension of the proximal interphalangeal (PIP) joint and compensatory flexion of the distal interphalangeal (DIP) joint. Boutonnière deformity is the opposite, featuring flexion of the PIP joint and hyperextension of the DIP joint. Ulnar deviation refers to the lateral deviation of the fingers at the metacarpophalangeal (MCP) joints. Z-thumb deformity involves hyperextension of the interphalangeal (IP) joint and flexion/subluxation of the metacarpophalangeal (MCP) joint of the thumb.
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