This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
Game Keeper's thumb is : 
Select and explain. 
A. Ulnar collateral ligament injury of MCP Joint, B. Radial collateral ligament injury of MCP joint, C. Radial collateral ligament injury of CMC joint, D. Ulnar collateral ligament injury of CMC joint
A: Ulnar collateral ligament injury of MCP Joint
Answer: A: Ulnar collateral ligament injury of MCP Joint 
Explanation: Injury to the ulnar collateral ligament of the thumb metacarpophalangeal joint is commonly referred to as gamekeeper's thumb or skier's thumb.
Injury occurs by fall on hand with forceful radial and palmar adduction of thumb as seen in skiers.
It is the most common injury of MCP joint.