Which ligament is primarily injured in gamekeeper's thumb?

Gamekeeper's thumb is an injury that specifically involves the ulnar collateral ligament (UCL) of the thumb. This ligament is crucial for stabilizing the metacarpophalangeal joint of the thumb, particularly during activities that involve gripping or pinching. The injury typically occurs when there is a forceful abduction of the thumb, which can happen in sports or activities that involve sudden twisting or stress on the thumb.

When the UCL is torn or sprained, it can lead to pain, swelling, and instability at the base of the thumb, severely affecting hand function. The symptoms often present as difficulty in gripping and reduced range of motion in the thumb, which is essential for many everyday tasks.

The other ligaments listed serve different functions. The radial collateral ligament supports the opposite side of the thumb and is not primarily associated with gamekeeper's thumb. The annular ligament encircles the radial head in the elbow, while the palmar ligament provides stability but is not specifically linked to the typical mechanism of injury seen in gamekeeper's thumb. Understanding the specific role of the ulnar collateral ligament in this context is key to grasping the injury's mechanism and implications for treatment.