Gamekeeper's thumb refers to injury of which ligament?

Gamekeeper's thumb refers to injury of which ligament?

• A. Radial collateral ligament of the thumb MCP
• B. Ulnar collateral ligament of the thumb (MCP joint)
• C. Annular ligament of the thumb
• D. Ulnar collateral ligament of the index finger MCP

Answer: (B)

Gamekeeper's thumb is a injury to the ulnar collateral ligament of the thumb’s metacarpophalangeal joint. This ligament on the ulnar (inside) side of the MCP joint stabilizes the thumb when it is gripped and tested against sideways (valgus) stress. When the thumb is forcefully abducted or hyperextended—such as catching a fall or during skiing—this ligament can tear or avulse from its attachment. The result is pain and instability at the base of the thumb, especially with pinching or grasping. A key nuance is that a complete tear can be complicated by a Stener lesion, where the adductor pollicis tendon interposes between the torn ligament and its insertion, often requiring surgical repair. Partial tears may heal with immobilization. Other options don’t fit because they involve different structures or joints: the radial collateral ligament of the thumb MCP is the opposite side, the annular ligaments are part of the flexor pulley system, and the ulnar collateral ligament of the index finger MCP is a different joint altogether.

Gamekeeper's thumb is a injury to the ulnar collateral ligament of the thumb’s metacarpophalangeal joint. This ligament on the ulnar (inside) side of the MCP joint stabilizes the thumb when it is gripped and tested against sideways (valgus) stress. When the thumb is forcefully abducted or hyperextended—such as catching a fall or during skiing—this ligament can tear or avulse from its attachment. The result is pain and instability at the base of the thumb, especially with pinching or grasping.

A key nuance is that a complete tear can be complicated by a Stener lesion, where the adductor pollicis tendon interposes between the torn ligament and its insertion, often requiring surgical repair. Partial tears may heal with immobilization.

Other options don’t fit because they involve different structures or joints: the radial collateral ligament of the thumb MCP is the opposite side, the annular ligaments are part of the flexor pulley system, and the ulnar collateral ligament of the index finger MCP is a different joint altogether.