You Asked: Why does it hurt when you hit your funny bone?

If you hit your elbow just right, chances are you’ll suddenly feel a sharp pain and unpleasant prickling sensation radiate down your arm. You may even exclaim a few choice words about your situation out of sheer agony and surprise. It’s true: A knock to the ‘funny bone’ is anything but funny.

Surprisingly, the funny bone isn’t really a bone at all. It’s actually a cluster of nerves called the ulnar nerve—a bundle of sensitive fibers that run behind your elbow joint. The ulnar nerve starts in the spine and offshoots through the shoulder and down the arm, ending in both the pinky finger and ring finger. It then follows a delicate pathway that is unprotected as it passes behind the knob of the elbow.

“The ulnar nerve is wedged between the bone and the skin near the elbow joint with little to no cushion or protection,” said Cody Bruce, MSN, RN, assistant professor with the Texas A&M Health Science Center College of Nursing. “When your elbow is extended, this area is protected, but, if the elbow is bent, it opens up this sensitive area. When you hit that groove, you’re actually pinching the nerve, which is why you experience moderate discomfort and a tingling feeling down the arm.”

According to the American Academy of Orthopedic Surgeons, the ulnar nerve controls most of the small muscles in the hand and wrist that coordinate fine movements, plays a fundamental role in function and coordination, and is responsible for delivering sensation to the pinky and ring fingers while directing the bigger forearm muscles to aid in grip strength.

Sometimes funny bone pain can be more serious than simply striking your elbow at the wrong angle. Persistent discomfort may signal a chronic health condition called “cubital tunnel syndrome,” which happens when the ulnar nerve is subjected to constant pressure or stretching.

Direct pressure (like flattening the arm against a desk or arm rest) can squash the ulnar nerve resulting in a pins-and-needles sensation, as if the hand or arm has fallen “asleep.” Keeping the elbow bent for extended periods of time may also stretch the nerve—most common when we stay in one positon during sleep. Repeating snapping of the elbow (routine in sports like tennis and golf) is another culprit.

“Cubital tunnel syndrome shouldn’t be confused with carpal tunnel syndrome (which primarily affects the wrist),” Bruce said. “Symptoms of cubital tunnel syndrome include pain, loss of sensation, tingling and weakness—usually confined to the ring and small fingers. Texting has actually increased diagnosis of cubital tunnel syndrome in recent years because the arm stays in a fixed, bent position when people text.”

Bruce said cubital tunnel syndrome normally affects the dominant arm, and if your arm or fingers become numb or tingly while texting, or in a bent position, you should straighten your arm out to bring blood flow and circulation back to the area. If the uncomfortable feeling persists, you may need to consult with your health care provider for treatment options.

Through history, it’s still unclear as to how the ulnar nerve was dubbed the funny bone. Bruce said one reason the name stuck is because of the dull tingling or funny sensation that occurs when the area is irritated. Others believe it’s a play on words, since the upper arm bone that runs between the elbow and shoulder is called the humerus. “One thing is clear: The funniest thing about the funny bone is it’s the only ‘bone’ in the body you can’t break, because it’s a nerve,” Bruce said.