When you accidentally strike your elbow, a unique sensation often shoots down your arm, leading to temporary tingling or a mild shock. This common experience, known as “hitting your funny bone,” prompts questions about its nature and the origin of its unusual name.
What is the “Funny Bone” Really?
Despite its common name, the “funny bone” is not actually a bone. It refers to the ulnar nerve, one of the three major nerves in the arm. This nerve originates from the spinal cord, travels down the arm, and extends into the hand, providing both motor control and sensation to certain fingers. Most of its length is protected by muscle, fat, or bone.
However, as the ulnar nerve passes through the elbow joint, it traverses a narrow channel called the cubital tunnel. At this specific point, the nerve lies directly behind the bony prominence on the inner side of the elbow, known as the medial epicondyle of the humerus. With only skin and a thin layer of tissue covering it, the ulnar nerve becomes exposed to impact. This exposed location makes it susceptible to direct pressure or compression against the underlying bone.
Why Does it Feel So “Funny”?
The distinctive sensation experienced when the “funny bone” is struck results from the direct stimulation or compression of the ulnar nerve. Unlike other injuries where pain signals originate from damaged tissue, hitting this spot irritates the nerve itself. This irritation causes the nerve to send a rush of signals down its pathway, leading to a feeling often described as tingling, numbness, pain, or “pins and needles.”
The sensation radiates along the nerve’s distribution, extending down the forearm to the pinky finger and the adjacent half of the ring finger. This “electric shock-like” feeling occurs because the nerve, when directly impacted, temporarily malfunctions, disrupting the normal flow of sensory information. While the sensation can be intense and momentarily disorienting, it usually subsides within a few minutes as the nerve recovers from the transient compression.
The Origin of the Nickname
The origin of the nickname “funny bone” has two primary theories. One theory suggests the name stems from the “funny” sensation that arises upon impact. The tingling, shocking feeling is so unusual that people simply described it as “funny.” This explanation highlights the unique physiological response as the basis for the term.
A more widely accepted theory attributes the name to a linguistic pun. The ulnar nerve, at the elbow, passes near the humerus, the long bone of the upper arm. Since “humerus” sounds similar to “humorous,” meaning amusing or funny, the term “funny bone” is believed to be a playful word association. This clever wordplay likely contributed to the nickname’s popular adoption.