Skier’s thumb is a common term often used to describe an injury to the ulnar collateral ligament of the thumb. While skiers often suffer these hand injuries, baseball players and many other athletes suffer them as well.

In this post, I discuss this difficult thumb injury, how a surgeon makes the diagnosis and whether a patient needs surgery to repair it.

The ulnar collateral ligament (UCL) of the thumb

The ulnar collateral ligament is a thick ligament on the metacarpophalangeal (MCP) joint of the thumb. It is the joint at the base of the thumb where it joins the long metacarpal bone just below it. The ulnar collateral ligament stabilizes the side of that joint closest to the other four fingers.

Mechanism of injury

Athletes often suffer this injury with a sudden valgus stress placed on the thumb. Essentially a force pulls the thumb away from the other four fingers. A skier might fall and land on the hand. The ski pole forces the thumb away from the fingers. A baseball player sliding into a base headfirst and catching the thumb on the base or a basketball hitting the thumb are common mechanisms for this injury as well.

Symptoms of a skier’s thumb injury

The patient might notice swelling of the thumb, especially at the base of the thumb. He might also have pain at the metacarpophalangeal joint on the ulnar side (side closest to the other four fingers). He might also have difficulty or pain moving the thumb.

Exam test for skier's thumb, or a UCL injury

Diagnosis of this thumb injury

A hand surgeon can examine the thumb and determine that the UCL is injured. By putting a valgus stress on the metacarpophalangeal joint and observing the joint opening up much more than the opposite thumb, he can detect a partial or complete tear of the ligament. He might order x-rays as well. X-rays are negative when the ligament has ruptured, but they can show a fracture if the ligament has pulled off a small piece of bone instead.


For complete tears of the ulnar collateral ligament with laxity of the metacarpophalangeal joint, the surgeon often repairs the ligament through a small incision. If there is a small bony avulsion, the surgeon might hold the fracture in place with pins or screws. While the surgery is fairly short, healing of the reattached ligament can take many weeks.

If you sprain your thumb in sports, you might consider seeing a hand surgeon for evaluation. If you do have an ulnar collateral ligament injury of your thumb, quick and proper treatment is very important.

Also read:
UCL injury of the thumb

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