The hand has several nerves that provide movement and sensation. The three main nerves of the hand are the ulnar, median and radial nerves. The ulnar nerve actually starts at the side of the neck, where nerves are connected to the spine and exit through small openings between the vertebrae. The ulnar nerve travels through the shoulder, down the arm and around the elbow, terminating in the hand.

The ulnar nerve supplies feeling to the little finger and half the ring finger. It works the muscle that closes the thumb into the palm and controls several other small muscles in the hand.

The problem occurs where the ulnar nerve passes around the elbow. The nerve rests in a groove called the cubital tunnel tucked behind the medial epicondyle, the bony point on the inside edge of the elbow (see diagram below). The cubital tunnel consists of muscle, ligament and bone. You can feel it if you straighten out your arm, turn your palm up, and gently rub the groove on the inside corner of your elbow. If you tap that groove and hit the ulnar nerve, you will experience small "electric shocks" up your arm into your hand.

(Image from University of Florida Department of Neurosurgery)

See also:
Cubital Tunnel Diagram