When people start to fall, they usually extend their arm to reduce the force of the impact when they hit the ground. If you try to break your fall on the palm of your hand or take a spill on the slopes with your hand strapped to a ski pole, your thumb may be injured.

Causes
The main ligament (ulnar collateral), which supports pinch and grasp activities, may be torn (sprained). The ligament helps your hand function properly, acting like a hinge to keep your thumb joint (metacarpophalangeal) stable.

Symptoms
When you have a sprained thumb, you lose some or all of your ability to grasp items between your thumb and index finger. It may or may not hurt right away. Other signs include bruising, tenderness and swelling. To make sure your injury does not cause long-term weakness, pain and instability, see your doctor for evaluation and treatment.

Treatment
If you have a partial tear, your doctor will probably immobilize your thumb joint with a splint or other bandage until it heals. You will wear the splint for about three weeks straight, at which point you will start taking it off to do flexion and extension exercises with your thumb. Put the splint back on for protection when you are not doing the exercises. Keep doing your exercises for another two or three weeks until your thumb's swelling and tenderness are gone. You may also put ice on your injury twice a day for 2-3 days after the fall.

Surgical Options
If your thumb ligament is completely torn, you may need surgery. Fragments of bone that sometimes get pulled away when your ligament tears may be removed or put back in their correct positions. After surgery, you'll probably need to wear a short-arm cast or a splint to protect your thumb ligament for six to eight weeks while it heals.