Skier's (Gamekeeper's) Thumb

Skier's thumb is a tear of the ligament on the inner side of your thumb's main knuckle (the joint where the thumb meets the hand). The classic mechanism is exactly what the name suggests: a ski pole strap catches the thumb and yanks it sideways during a fall. The ligament is called the ulnar collateral ligament (UCL) — it's what stops your thumb from bending too far away from your other fingers and what gives a strong pinch its stability. Gamekeeper's thumb is the same injury when it happens slowly over time from chronic strain, named after the British game wardens who used to wring rabbits' necks. When the UCL tears all the way through, your thumb feels weak, painful, and unstable when you try to pinch or grip.

There's one specific pattern that always needs surgery: a Stener lesion. That's when the torn end of the ligament has flipped over and gotten stuck on the wrong side of a nearby muscle sheath. In that position the ligament physically can't reach back to its attachment to heal on its own — surgery is the only way it gets fixed.

• Pain and swelling on the inner side of the thumb's main knuckle (the MCP joint) after a fall or forceful bending
• Weakness of pinch grip — trouble turning a key, opening a jar, or holding a piece of paper between your thumb and index finger
• A feeling of looseness or instability when you pinch or grip
• Bruising along the inner edge of the thumb
• Tenderness right over the ligament when you press on the inner side of the knuckle
• Pain that worsens when the thumb is bent sideways away from the other fingers

Your provider gently bends your thumb sideways to test the ligament — comparing how much it gives compared to your other hand. A wide gap (more than about 35 degrees, or 15 degrees more than the opposite side) means a complete tear. Stress X-rays confirm the diagnosis, and an MRI can identify a Stener lesion before surgery — important because that finding shifts the plan from cast to operating room.

Complete UCL tears and any Stener lesion need surgery. The repair stitches the torn ligament back to its attachment point, often anchored with a small bone anchor. Without surgery, a complete tear leaves the thumb chronically weak and unstable — you lose much of your pinch strength permanently.

External patient-education references and related OSI pages for additional background:

• Britannica — Hand (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language