Why your funny bone isn't funny

The 'funny bone' is a nerve, not a bone. Find out where it runs and why knocking it hurts so much.

4 minutes · 5 stops

It isn't a bone at all
The "funny bone" is the ulnar nerve, which runs from your neck to your little finger. At the back of your elbow it passes through a groove with almost nothing protecting it, so a knock squashes it against the bone.
The bone it rests on
The nerve slides behind a bony bump on the inner end of the humerus, your upper arm bone. Some people think the name is a pun on "humerus" and "humorous", though nobody knows for sure where it came from.
Where the nerve starts
The ulnar nerve begins in a tangle of nerves in your neck and armpit called the brachial plexus. Nerve roots from your spinal cord join, split and rejoin here, then head down the arm as separate nerves.
What it controls
Below the elbow, the ulnar nerve powers most of the small muscles inside your hand, the ones that spread your fingers and give you fine control. That is why damage to it makes delicate tasks like doing up buttons difficult.
Why it tingles in your little finger
The nerve also carries feeling from your little finger and half your ring finger. When you bump your elbow, your brain thinks the signal came from those fingers, so that is where you feel the zing. Leaning on your elbows for a long time can make them tingle too.