Funny bone

What is the funny bone?
C. Noel Henley, MD

The funny bone is not a bone – it’s a nerve called the ulnar nerve, which travels on the back side of your arm (where your triceps muscle is) and around the inner part of the elbow into your forearm.

The nerve is mostly unprotected where it lays in a groove between the ulna and humerus bones. It comes out of muscle, rests right on bone, then goes back underneath muscle.

The ulnar nerve supplies the pinkie and ring fingers with nerve fibers – sensation and muscle function. When you hit your funny bone, you’ll feel tingling in these two fingers.

Testing the funny bone

Hand surgeons and orthopaedic specialists test the ulnar nerve for problems by tapping on the nerve. If you have tingling when tapping on your funny bone, it’s a signal of nerve sensitivity. This may come and go, and isn’t necessarily an alarming thing.

When you spread your fingers apart – you’re testing the ulnar nerve!

Cubital tunnel syndrome – a pinched nerve problem

As the ulnar nerve passes from the back side of the arm into the forearm, it takes a sharp turn around the humerus bone. It’s covered by a strong layer of tissue called fascia.

When you bend or flex your elbow (when talking on the phone for example), this increases pressure on the ulnar nerve, which can cause a numbness or tingling sensation in the hand or forearm. Straightening the elbow usually relieves it.

Persistent numbness is not a good sign, and sometimes surgery is necessary to relieve the pressure on the nerve and restore hand function and sensation. Read more about cubital tunnel syndrome.

If you hit your funny bone harder than usual

If you hit your funny bone especially hard, it can cause enough bruising and swelling to compress and pinch the nerve. If the numbness lasts more than a few days, see a hand or orthopaedic doctor.

Usually treatment of a nerve bruise involves keeping a close eye on your hand function and not ignoring your symptoms. This kind of nerve injury usually recovers on its own but splinting and therapy may help.

The not so funny bone

Nerves branch out from the spine to other body parts like hundreds of tree branches. The tiniest branches are in the pinkie fingertip – those nerve fibers come from the larger trunk of the ulnar nerve.

Even though hitting your funny bone isn’t a joking matter, at least next time you’ll appreciate its purpose and function a little more.