A tear/sprain to the ulnar collateral ligament at the bottom of the thumb. Also known as a gamekeeper's thumb.
Skier’s thumb is caused by trauma, usually a fall on an outstretched hand forcing the thumb out, tearing the ligament at the inside by the web space. The classic example is the skier holding a ski pole in hand, falling on hard snow, pushing the pole hard up against the inside of the thumb.
You may feel a snapping sensation at the inside of the thumb, followed by pain and swelling. The pain will be located at the inside of the thumb by the web of the hand, and may be painful to the touch. The pain will worsen with movement, and you may see a black or blue area forming at the base of the thumb.
Depending on the severity, the ligament may be surgically pinned back in place, and you will be in a cast while it heals. After the pin is removed, scar massage and scar management techniques will be implemented to keep the scar from sticking to the softer tissue underneath. A hard custom orthotic will give you continued protection after the splint is removed and prevent the thumb from going out again. Range of motion exercises will follow and eventually, exercise to regain lost strength and function.