We’ve all hit our elbow a rough couple of times before, so you must remember what follows: a gripping tingling suddenly engulfs your whole arm in tandem with excruciating pain. It all feels like a million volts of electricity just passed through you. Usually, this numbness only lasts a couple of minutes, but if it doesn’t go away then this is the case for a doctor. If you ever wondered what causes this strange sensation, read on.

It’s not funny

The region right below the elbow is called the funny bone, but when you get hurt there it’s anything but funny. It’s not a bone either, but a nerve called 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 ulnar nerve is one of the three main nerves in your arm. Since it’s such a long nerve, filled with many branch-like ramifications, there are some key areas where it can get constricted. Sometimes the ulnar nerve gets compressed at the wrist, beneath the collarbone, or as it comes out of the spinal cord in the neck, but the most common place the ulnar nerve gets constricted is below the elbow.

Ulnar nerve palsy. Orthopaedic Knowledge Online 2009

For most of its length, the ulnar nerve is protected, like rest of the body’s nerves, by bones, muscles and/or ligaments. As the nerve passes the elbow, though, it runs through a channel called the cubital tunnel, and here it’s protected only by skin and fat. The cubital tunnel runs through bony bump called the medial epicondyle. The spot where the nerve runs under the medial epicondyle is commonly referred to as the “funny bone.” At the funny bone the nerve is close to your skin, and bumping it causes a shock-like feeling.

The ulnar nerve runs behind the elbow on the inside of the arm. Credit: Orthoinfo

Past the elbow, the ulnar nerve gently crosses muscles beneath your forearm and into your hand on the side of the palm. Here, the nerve supplies the pinkie and ring fingers with nerve fibers, which is why these feel tingly when you hit your elbow. It also controls most of the little muscles in the hand that help with fine movements, and some of the bigger muscles in the forearm that help you make a strong grip.

Cubital Tunnel Syndrome

It’s not sudden shocks to your elbow that can cause pain. Flexing or bending your elbow for prolonged periods of time increases pressure on the ulnar nerve, which can cause a numbness or tingling sensation in the hand or forearm. Because this can irritate the nerve, keeping your elbow bent for long periods or repeatedly bending your elbow can cause painful symptoms. For example, many people sleep with their elbows bent. This can aggravate symptoms of ulnar nerve compression and cause you to wake up at night with your fingers asleep. If you feel pain for weeks onward following an injury, visit a doctor fast.