Causes / typical injury mechanism: Thumb collateral ligament injuries arise as a result of stress to the metacarpophalangeal (MCP) joint. Ulnar collateral ligament (UCL) injuries are more common and occur as a result of radial (valgus) stress. Radial collateral ligament (RCL) injuries are rarer and occur as a result of ulnar (varus) stress. (The mechanism is opposite the ligament.) The Stener lesion represents the retracted proximal aspect of the torn UCL, which can become entrapped in the insertion of the adductor pollicis aponeurosis.

Classic history and presentation: The condition presents as pain in the region of the MCP joint following a fall onto an outstretched hand. It commonly presents as a sports injury, most frequently seen in sports that involve racket use or ball handling. UCL injuries can occur in a skier who falls with the pole still strapped to their hand. The patient with an acute injury may report an abduction or valgus stress to the thumb at the time of injury and may present with pain, swelling, and reduced range of motion at the thumb MCP joint. A palpable mass representing a Stener lesion may or may not be present. The patient may have difficulty with pinch or grasp maneuvers such as opening jars and turning keys.

Prevalence: Thumb collateral ligament injuries are common and have been estimated to account for approximately 50 per 100 000 ED visits.

Risk factors:  Risk factors include racket sports, sports involving ball handling, and other activities that place an individual at risk for a fall onto an outstretched hand. Skiing also poses a risk for UCL injuries.