What is it?
The ulnar collateral ligament is a strong band of tissue that resists separation of the thumb from the index finger. An ulnar collateral ligament sprain is a stretch or tearing of the ulnar collateral ligament. Acute sprains of the ulnar collateral ligament can occur when the thumb is pulled away from the index finger. This is a common injury in skiing, due to gripping the ski pole during a fall, so it may be referred to as a “skier's thumb”. It may also occur after falling on an outstretched thumb or hooking a thumb into a jersey or facemask.

Symptoms
Symptoms of an ulnar collateral ligament injury include pain over the inside of the thumb and pain with movement of the thumb. There may also be swelling. There can be decreased pinch strength, making holding objects between the thumb and index finger difficult.

Sports Medicine Evaluation
Work-up for a suspected ulnar collateral ligament injury begins with an examination of the injured wrist, hand, and thumb, as well as the uninjured wrist, hand, and thumb. This may include evaluation for tenderness over the inside of the thumb, usually near the base, as well as testing how loose the ligament is by bending the thumb away from the index finger. Imaging may be ordered to assist with diagnosis. X-rays should be performed, and an ultrasound or magnetic resonance imaging (MRI) may also be done.

Treatment
Treatment depends on severity of the injury. Sprains are graded as Grade I, II, or III. Grade I represents minimal stretching. Grade II represents more significant stretching or tearing. Grade III represents a complete tear. Grade I and II injuries can usually be treated by preventing thumb movement with a cast, taping, or splinting for up to 6 weeks. This may be accompanied with antiinflammatory medications, ice, and elevation. A Grade III injury may require surgical repair. Rehabilitation is commonly required as well.

Injury Prevention
Most of these injuries occur as accidents that cannot be prevented. Ski poles that are strapless or have breakaway straps do not seem to decrease the risk of injury.

Return To Play
Return to play should be overseen by a sports medicine physician to ensure safe and timely return to sport. Most physicians will decide an athlete is ready to return to play once the thumb has full strength, pain-free full range of motion and ability the ability to protect the thumb during activity. This can take varying amounts of time, but on average about 6-8 weeks.

AMSSM Member Authors: Mark Kasmer, MD, Matt Gammons, MD

References
Brukner P, Khan K. Brukner & Khan’s Clinical Sports Medicine. 4th Edition. Australia: McGraw-Hill Education; 2012.

Eiff MP, Hatch R. Fracture Management for Primary Care. 3rd Edition. Philadelphia, PA: Elsevier Saunders; 2012.

Ritting AW, Baldwin PC, Rodner CM. Ulnar collateral ligament injury of the thumb metacarpophalangeal joint. Clin J Sport Med. 2010 Mar;20(2):106-12.

Rouzier P. The Sports Medicine Patient Advisor. 3rd Edition. Amherst, MA: Sportsmed Press; 2010.