Why Does Hitting Your “Funny Bone” Feel Like That?

There’s nothing humerus about it:

No, seriously:

There really is nothing humerus about it, because the humerus is the long bone in your upper arm, while the long bones in the lower arm are the radius and ulna, and this sensation has to do with the ulnar nerve, which runs down the (you guessed it) ulna.

As for what’s going on anatomically: across from the medial epicondyle (which latter feature is part of the adjacent humerus), the ulnar nerve passes through the cubital tunnel and becomes much less protected than along the rest of its path. Further, bending your elbow flattens the ulnar nerve against the bone, displaces surrounding tissue, and leaves the nerve covered mainly by skin and ligament, making it easier to strike.

As a result, a blow to this area stimulates the nerve fibers themselves, causing a burst of nerve signals that produces the intense pins-and-needles sensation known as transient paresthesia, which radiates down your forearm into outermost fingers.

Worse, repeated pressure on the bent elbow can compress the ulnar nerve in the cubital tunnel, trapping the nerve there and leading to chronic tingling, numbness, pain, and weakness in your forearm and hand. This is called cubital tunnel syndrome.

Rarely, an unusually forceful impact has occasionally caused temporary loss of consciousness, possibly by briefly disrupting nerve signaling and blood flow.

Happily, you can reduce the risk: if you regularly straighten your elbows, stretch your arms, avoid prolonged elbow flexion or leaning on your elbows, and take frequent breaks to relieve pressure and maintain healthy blood flow to the ulnar nerve, your chances of coming to harm are very slim.

For more on all of this delightful topic, enjoy:

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Take care!