Why does your funny bone hurt when you hit it?
The short answer
When you hit your funny bone at just the right angle, you’re actually hitting the ulnar nerve, one of the three primary nerves running down your arm. The sharp, tingling pain you feel is because the nerve is being pressed or pinched.
The long answer
Your "funny bone" isn't really a bone at all, but rather a nickname for a sensitive area around your elbow. If you've ever accidentally bumped this spot, you know it results in a strange, painful sensation that shoots down your arm, causing your fingers to tingle. But why does hitting your funny bone hurt so much?
When you hit your funny bone, you're really striking the area around your bent elbow, called the cubital tunnel. This narrow channel houses the ulnar nerve, which runs from your neck, down your arm, and all the way to your hand, affecting your forearm, pinky, and ring fingers. Unlike most nerves in your body, the ulnar nerve is only protected by a thin layer of skin and a small amount of fat at the elbow joint, making it especially vulnerable.
When you strike your elbow in this spot, you essentially squeeze or compress the ulnar nerve against the medial epicondyle, a bony bump on the inside of your elbow. This compression is what sends that sudden, electric shock-like sensation racing down your arm.
"Ulnar Nerve" by BruceBlaus is licensed under CC BY 4.0
The reason why hitting your funny bone feels so different from the pain of stubbing your toe, for example, is because it’s simply a different pain sensation.
Stubbing your toe results in nociceptive pain, which is caused by damage to tissues and sends signals to the brain saying, "Stop that!" The funny bone feeling is actual nerve pain (often called neuropathic pain) from your ulnar nerve and results in a combination of sharp stings, numbness, and that weird "pins and needles" feeling.
Sources
McCallum, K. (2021, February 24). Why Does Hitting Your Funny Bone Hurt So Much? Houston Methodist: On Health. Retrieved September 13, 2022, from https://www.houstonmethodist.org/blog/articles/2021/feb/why-does-hitting-your-funny-bone-hurt-so-much/
Neurosurgical Associates of Central Jersey. (2017, May 15). The Funny Bone (aka the Ulnar Nerve) Is No Laughing Matter. Neurosurgical Associates of Central Jersey. Retrieved September 13, 2022, from https://neurosurgerycnj.com/the-funny-bone-aka-the-ulnar-nerve-is-no-laughing-matter/