Which injury is defined by tearing of the ulnar collateral ligament at the MCP joint of the thumb?

Which injury is defined by tearing of the ulnar collateral ligament at the MCP joint of the thumb?

• A. Jersey finger
• B. Mallet finger
• C. Gamekeeper's (skier's) thumb
• D. Boutonnière deformity

Answer: (C)

The injury described is a tear of the ulnar collateral ligament at the metacarpophalangeal joint of the thumb, which is known as Gamekeeper's thumb (also called skier's thumb). The ulnar collateral ligament stabilizes the thumb’s MCP joint during pinching, and an abnormal force—such as forced abduction or a fall onto an outstretched thumb—can stretch or rupture this ligament. This injury specifically affects the thumb at its base joint (MCP), not the fingers, and presents with pain and instability when trying to pinch or grip. The other conditions involve different structures: Jersey finger is a rupture/avulsion of the flexor digitorum profundus tendon at the fingertip; Mallet finger is an extensor tendon avulsion at the distal interphalangeal joint; Boutonnière deformity is a central slip injury at the proximal interphalangeal joint. Thus, tearing of the UCL at the thumb’s MCP joint fits Gamekeeper’s thumb best.

The injury described is a tear of the ulnar collateral ligament at the metacarpophalangeal joint of the thumb, which is known as Gamekeeper's thumb (also called skier's thumb). The ulnar collateral ligament stabilizes the thumb’s MCP joint during pinching, and an abnormal force—such as forced abduction or a fall onto an outstretched thumb—can stretch or rupture this ligament. This injury specifically affects the thumb at its base joint (MCP), not the fingers, and presents with pain and instability when trying to pinch or grip. The other conditions involve different structures: Jersey finger is a rupture/avulsion of the flexor digitorum profundus tendon at the fingertip; Mallet finger is an extensor tendon avulsion at the distal interphalangeal joint; Boutonnière deformity is a central slip injury at the proximal interphalangeal joint. Thus, tearing of the UCL at the thumb’s MCP joint fits Gamekeeper’s thumb best.