If you’ve ever bumped your elbow and felt a tingling sensation down your arm into your hand (hitting your "funny bone"), you’ve bumped the ulnar nerve. But the ulnar nerve also can be the cause of more serious and permanent problems in the fingers and hand.
The ulnar nerve extends down the arm, across the elbow, and into the hand. It provides sensation to the little and ring fingers and activates many of the small muscles in the hand. You can actually feel this nerve as it passes behind the elbow and through a tight tunnel (the cubital tunnel) at the inside of the elbow.
The problem An injury to the elbow such as a dislocation or fracture can tear or inflame the ulnar nerve. The inflamed nerve can swell and become trapped in the cubital tunnel. This gives the condition its name, ulnar nerve entrapment. It is often also called cubital tunnel syndrome.
Prolonged pressure on the nerve also can be a problem. Bending the elbow stretches the ulnar nerve and puts pressure on it as it passes through the cubital tunnel, pressing it against the bone. This constant rubbing can damage the nerve’s protective covering (myelin sheath) or the nerve itself and disrupt the nerve’s ability to conduct messages from the brain. Gradually, the muscles of the hand start to weaken, so that it becomes difficult to open a jar or grasp a tool.
http://www.mconcannon.com/hand/ulnar-info.php
