A skier sustains a fall and pain at the base of the thumb; which ligament at the 1st MCP is most likely injured?

A skier sustains a fall and pain at the base of the thumb; which ligament at the 1st MCP is most likely injured?

• A. 2nd MCP joint UCL
• B. 1st MCP joint UCL
• C. 3rd MCP joint UCL
• D. 5th MCP joint UCL

Answer: (B)

The key idea is that the injury pattern fits a tear of the ulnar collateral ligament at the thumb’s metacarpophalangeal joint. When the thumb is forcibly abducted during a fall onto an outstretched hand, the ligament on the ulnar side of the 1st MCP joint can rupture. This produces pain at the base of the thumb and instability on valgus stress testing, which is classic for damage to the UCL of the 1st MCP joint (often called skier’s or gamekeeper’s thumb). The other MCP UCL injuries involve different digits and mechanisms, so they don’t fit this scenario as well.

The key idea is that the injury pattern fits a tear of the ulnar collateral ligament at the thumb’s metacarpophalangeal joint. When the thumb is forcibly abducted during a fall onto an outstretched hand, the ligament on the ulnar side of the 1st MCP joint can rupture. This produces pain at the base of the thumb and instability on valgus stress testing, which is classic for damage to the UCL of the 1st MCP joint (often called skier’s or gamekeeper’s thumb). The other MCP UCL injuries involve different digits and mechanisms, so they don’t fit this scenario as well.