With spooky season in full swing, houses are adorned with carved pumpkins, bedsheet ghosts, and decorative skeletons. The latter always catch my eye due to their poor anatomical accuracy. Even worse are some of the names that people give the bones in the body — for example, the ‘funny bone’ which is often used when referring to the long bone in the arm.
Whether the name comes from the homophones (words having the same pronunciation but different meanings) ‘humerus’ and ‘humorous’, or from that funky tingling sensation you get from hitting your elbow, the term ‘funny bone’ is quite clever! But there’s one drawback: the pain actually comes from hitting a nerve not a bone.
The humerus is the long bone that connects your shoulder to your elbow; it attaches to the scapula on one end, and your ulna and radius at the other. If you find the bony part of your elbow (the olecranon), and then move your fingers a bit inwards (towards your torso), you’ll feel a second bony point called the medial epicondyle. This is the one of the rounded ends of the humerus. The valley between these points is called the cubital tunnel, and that’s where the ulnar nerve passes through.
This nerve originates from the spinal cord, passes under the collar bone, continues along the inside of your upper arm, and then runs through this tunnel, where it’s susceptible to getting hit. That’s because the rest of the nerve is protected by layers of muscle, fat, and other tissues, but in the cubital tunnel, there’s much less protection. If you gently press inside that valley, you’re feeling the ulnar nerve!
Image source: https://ladanhajipour.com/conditions/hand/cubital-tunnel-syndrome/
After passing the elbow, the ulnar nerve continues towards — you guessed it — the ulna. Here, it branches to give innervation to many of the muscles in your forearm responsible for flexion, as well as the fourth and fifth fingers. That’s why when you hit the ‘funny bone’ the tingling runs down your arm and all the way into your fingers.
While elbowing something hard can leave you feeling unpleasant for a minute or so, more serious complications like pinching or compressing the ulnar nerve is no laughing matter.
