Background: Injury to the ulnar collateral ligament (UCL) of the first metacarpophalangeal joint (MCPJ) is a common injury, especially in skiers. It is often misdiagnosed, which can lead to chronic instability.
Objective: This article reviews the current literature on UCL injury of the thumb and describes the clinical assessment and management.
Discussion: The UCL of the thumb is often injured as a result of forced abduction of the thumb, with or without extension. The injury can be identified by pain, swelling and haematoma along the ulnar border of the first MCPJ as well as pain and laxity on valgus stress testing. Proper examination involves placing a valgus stress on the thumb and measuring instability. Initial investigation should involve a plain X-ray, supplemented by ultrasound or magnetic resonance imaging, where appropriate. Treatment can be conservative or involve surgical management depending on the severity of the injury.