Ulnar Neuritis
When the elbow is bent, the ulnar nerve stretches around the bony bump at the end of the humerus. In throwing athletes, the ulnar nerve is stretched repeatedly, and can even slip out of place, causing painful snapping. This stretching or snapping leads to irritation of the nerve, a condition called ulnar neuritis.
Throwers with ulnar neuritis will notice pain that resembles electric shocks starting at the inner elbow (often called the "funny bone") and running along the nerve as it passes into the forearm. Numbness, tingling, or pain in the small and ring fingers may occur during or immediately after throwing, and may also persist during periods of rest.
Ulnar neuritis can also occur in non-throwers, who frequently notice these same symptoms when first waking up in the morning, or when holding the elbow in a bent position for prolonged periods.