The ulnar collateral ligament is a strong band that is attached to the middle joint of the thumb (metacarpophalangeal joint). Injury to this ligament is also known as Gamekeeper’s Thumb, because Scottish gamekeepers used to commonly have this type of injury as a result of their jobs; and more commonly today as Skier’s Thumb, because it occurs so often in downhill skiing accidents. Injury to this ligament is commonly due to any hard force put on that thumb that causes the thumb to be pulled away from the palm of the hand, usually a result of a sports related injury. This force can result in a partial tear of the UCL (ulnar collateral ligament) or a complete tear of the UCL, known as a rupture. A tear to the UCL results in the MCP (metacarpophalangeal) joint of the thumb becoming very unstable and painful. The most common symptoms associated with UCL injuries are swollen, painful joint, and weakness to thumb especially with gripping or pinching, as well as bruising.