Dear Dr. Universe: Why do we have funny bones and why does it hurt so much when we hit that spot on our elbows? -Ms. Hundley and students

Dear Ms. Hundley and Students,

The human body is made up of 206 bones with different names. There’s your skull, or cranium. There’s your finger and toe bones, or phalanges. There’s also your kneecap, or patella. But it turns out, the bone we call the funny bone isn’t really a bone at all.

That’s what I found out from my friend Janessa Graves. She’s a researcher at Washington State University who knows a lot about the human body and studies injuries, like concussions in children.

Illustrated, cartoon cat with labcoatWhen you hit your funny bone, you are actually hitting part of a whitish bundle of fibers called a nerve. Your nerves help send messages from different parts of your body to the brain. Just as bones have different names, so do nerves. The one we feel when we hit our “funny bone” is the “ulnar nerve.”

Most nerves in the body usually have some kind of protection. Often they are cushioned by muscle or bone. But the ulnar nerve is a little different. Part of your ulnar nerve travels through a channel in your arm called the cubital tunnel. This leaves part of the nerve around your elbow a bit more exposed. It’s only protected by a bit of skin and fat.

When we hit our elbow just right on a corner or hard surface, that nerve gets squished, or compressed.

“This compression creates a painful, shocking, burning or tingling sensation that is pretty unique,” Graves said. “It shoots all the way down to the tips of our fingers, which is where the nerve ends.”

If you do hit your ulnar nerve, you’ll probably only feel those sensations for about 30 seconds or so. Even though it can be a bit painful, it doesn’t usually do much damage to the nerve. Graves adds that sometimes people do hit their funny bone and that feeling doesn’t go away, so they have to see a doctor to figure out exactly what might be going on.

Either way, it doesn’t seem like much of a laughing matter when you hit your funny bone. That made me wonder where it got its name. Graves said there are a few ideas about it.

One idea is that it’s because the ulnar nerve is next to a bone called the humerus bone, which runs from your shoulder to the elbow. Some people think the funny bone got its name because humerus sounds like humorous—it’s a homonym, or a word that sounds like another word but has a different spelling.

Another idea is that the sensation of hitting the nerve creates a funny or unusual feeling in our arm, hand, and fingers. I don’t know about you, but even though it is technically a nerve, I think I’ll stick to the tradition of calling it the funny bone.

Sincerely,
Dr. Universe