The short answer
Gamekeeper's thumb — its acute form is called skier's thumb — is a sprain or tear of the ulnar collateral ligament (UCL) at the base of the thumb, causing pain, swelling, and a weak, unstable pinch. Partial injuries are treated with bracing, hand therapy, and sometimes PRP; complete tears often need surgical repair, so accurate diagnosis with ultrasound matters.
Medically reviewed by Marc Gruner, DO, MBA, RMSK
Sports medicine physician, Mayo Clinic fellowship. Last reviewed June 2026
Overview
The ulnar collateral ligament stabilizes the thumb against pinch and grip. A forceful bend of the thumb away from the hand — from a fall onto a ski pole, a ball, or a handlebar — can sprain or tear it, producing pain, swelling, and a pinch that feels weak or unstable.
The key question is whether the ligament is partially or completely torn. Dr. Gruner uses ultrasound to grade the injury: partial injuries respond to bracing, hand therapy, and in some cases PRP, while complete tears (including a 'Stener lesion') generally require surgical repair for a stable, functional thumb.
Common symptoms
- Pain on the inner side of the thumb base
- Swelling and bruising
- Weak or unstable pinch
- Difficulty grasping or holding objects
What to expect at your visit
- 1.
A focused conversation
Dr. Gruner reviews your history, prior imaging, and goals — what you want to get back to doing.
- 2.
Point-of-care ultrasound
When useful, a diagnostic musculoskeletal ultrasound evaluates the injury in real time, with no radiation.
- 3.
A clear, individualized plan
You leave understanding the diagnosis, the non-surgical options, and the expected timeline — in plain language.
Frequently asked questions
- Does gamekeeper's thumb always need surgery?
- No. Partial UCL injuries usually heal with bracing, hand therapy, and sometimes PRP. Complete tears — especially a Stener lesion where tissue blocks healing — typically need surgical repair, which is why an ultrasound or exam to grade the tear is important.