What Happens When You Hit Your Funny Bone?

At some point in your life, you’ve hit your elbow against a piece of furniture at just the right angle, in just the right spot, and felt tingly nerves shoot down your forearm. If you’re especially lucky, you would have hit your arm hard enough to turn your smallest finger numb for the next few minutes. What is your funny bone, and why does it feel so different from regular pain, such as stubbing your toe?

What is your funny bone? And how do you hit it?

Contrary to its name, your ‘funny bone’ is not a bone, but a nerve. Specifically, it is the ulnar nerve, which originates from a network of nerves in the spinal cord of your neck, runs down your arm, and ends in your ring and pinkie finger. It is one of the three major nerves in your arm. Despite traversing from the armpit down to your fingers, the ulnar nerve provides very little function in your upper arm. Instead, it provides a major role in conveying sensory and motor information from the forearm and down. It controls muscle fibers from your forearm to your fingers, allowing you to grip objects, execute small muscle movements for fine motor control, and gives feeling to the area of your pinky finger and the parts of your palm and ring finger closest to your pinky finger.

Fig. 1: An illustration of the ulnar nerve across the entire arm.

Your nerves are carefully protected under several layers of fat, muscle, and tissue. However, there are areas where they can become exposed. At the complex junction of your elbow, the ulnar nerve travels through the cubital tunnel, a tunnel of muscle and ligament tissue, and behind the medial epicondyle, a bump-like structure in your humerus bone. 

When your elbow is bent, the protective tissue shifts to the side of the ulnar nerve, which is flattened against the medial epicondyle. As a result, the nerve is left exposed, with only thin ligament tissue and skin as padding. This leaves it susceptible, and when you hit your bent elbow at a precise angle, the ulnar nerve is squished against the bone, sending sparks down your arm. 

Fig. 2: A basic illustration of the bones and ligaments relevant to the ulnar nerve within the elbow.

Why does hitting your funny bone feel different from pain?

Your nervous system is composed of a wide range of neurons. Amongst them are your sensory receptors, which receive stimuli that your brain then interprets as sensory information. These include, but are not limited to, thermoreceptors, which detect changes in temperature, tactile receptors in your skin to detect pressure and touch, or nociceptors, which detect potential tissue damage that your brain registers as pain.

The ulnar nerve is not a sensory receptor, but a bundle of nerve fibers that carry information from sensory receptors and muscle tissue to and from the brain. It is not designed to receive external stimuli. When you hit your ‘funny bone’, rather than feeling pain from a nociceptor, you mechanically stimulate the ulnar nerve, producing the unique sensation of numbness and tingling shooting down your forearm. 

Can you seriously hurt yourself by hitting your funny bone?

Most bumps to the funny bone usually only result in temporary irritation. But, like most things in your body, if you hit yourself hard enough, something bad will happen. Likewise, if you hit your ulnar nerve with significant force, you risk damaging it. 

Sudden accidents, such as broken bones or dislocated elbows, can cause immediate tissue swelling, which then compresses the ulnar nerve over long periods of time, forming a pinched nerve. 

• Pinched nerve: This occurs when too much pressure is applied to a nerve by surrounding tissues, such as bones, cartilage, muscles, or tendons.

The proper terminology for a pinched ulnar nerve is ulnar nerve entrapment. We can then go even more specific: ulnar nerve entrapment is called cubital tunnel syndrome when it occurs at the elbow, or Guyon’s canal syndrome at the wrist. Repetitive pressure from prolonged elbow bending, arthritis, or casts and splints can also create a pinched nerve over several years. This can lead to numbness, hand weakness (eg, difficulty picking up objects), elbow pain, and curling of the pinky and ring fingers.

To maintain the health of your ulnar nerve, it is recommended to take regular breaks between extended periods of bending your arm and to practice stretches that target your wrist and elbow.

Fun Facts

• Because you hit the ulnar nerve itself, and not the bone, hitting your funny bone results in numbness shooting down your entire arm, rather than just your elbow.

• Like humans, many mammals also have ulnar nerves that they can accidentally hit.

• Cubital tunnel syndrome and the (more well-known) carpal tunnel syndrome are both forms of nerve entrapment, but occur in different areas (elbow vs wrist) and affect different nerves.

Summary

What have we learned? Your ulnar nerve is responsible for conveying movement and sensory information in your forearm and small fingers. When you hit your funny bone, you are actually hitting your ulnar nerve, rather than a sensory neuron, creating an unfamiliar tingling sensation. The ulnar nerve can become pinched when surrounding tissue is inflamed, resulting in numbness and weakness in the hand. Thus, don’t underestimate the importance of regular stretches for the health of your nerves.

Your body has an intricate system of nerves, muscles, and ligaments, all working together to keep your body functioning. But it never hurts to be a bit careful when you bend your elbow, lest you hit your ulnar nerve!

Reference List

Cleveland Clinic (2021). Ulnar Nerve: Anatomy, Function & Common Conditions. [online] Cleveland Clinic. Available at: https://my.clevelandclinic.org/health/body/21664-ulnar-nerve.

Cleveland Clinic. (n.d.). Ulnar Nerve Entrapment: Causes, Symptoms & Treatment. [online] Available at: https://my.clevelandclinic.org/health/diseases/22272-ulnar-nerve-entrapment.

Goldman, J.G. (2015). Why does it hurt so much to hit your funny bone? [online] www.bbc.com. Available at: https://www.bbc.com/future/article/20150827-why-does-it-hurt-so-much-to-hit-your-funny-bone [Accessed 21 Aug. 2025].

Jones, O. (2019). The Ulnar Nerve - Course - Motor - Sensory - TeachMeAnatomy. [online] Teachmeanatomy.info. Available at: https://teachmeanatomy.info/upper-limb/nerves/ulnar-nerve/ [Accessed 21 Aug. 2025].

Mayo Clinic (2023). Pinched nerve - Symptoms and causes. [online] Mayo Clinic. Available at: https://www.mayoclinic.org/diseases-conditions/pinched-nerve/symptoms-causes/syc-20354746.

TED-Ed (2024). Why does hitting your funny bone feel so horrible? - Cella Wright. YouTube. Available at: https://www.youtube.com/watch?v=IwYut9qF-jM.

Turito.com. (2023). Types of Signals- Sensory Receptors and Classification. [online] Available at: https://www.turito.com/learn/biology/types-of-signals [Accessed 31 Aug. 2025].