1. Mallet finger. Extensor tendon avulsion with or without fracture involving the distal interphalangeal (DIP) joint. The athlete cannot extend the DIP joint.
2. Jersey finger. Avulsion of the flexor digitorum profundus tendon causing inability to flex the DIP joint. Usually occurs from grabbing a jersey when tackling in football.
3. Gamekeeper’s thumb. Rupture of the ulnar collateral ligament of the first metacarpophalangeal (MCP) joint. Frequent in skiing injuries.
4. Boxer’s knuckle. Longitudinal tear of the extensor digitorum communis tendon or sagittal bands overlying the metacarpal head (usually the third MCP), resulting in extensor weakness of that finger and, at times, painful extensor tendon subluxation.