Hitting your “funny bone” is a common experience, causing a sudden, jarring sensation in the elbow. This peculiar feeling, often described as tingling or a jolt, has led to the widespread phrase “hitting your funny bone.” Despite the name, this sensation doesn’t involve a bone at all.
The Ulnar Nerve: Your “Funny Bone”
The “funny bone” is actually the ulnar nerve. This nerve courses along the inner side of the elbow, specifically passing through a groove located behind the medial epicondyle, the prominent bony bump on the inside part of your elbow. Its superficial position in this area, without significant muscle or bone protection, makes it particularly susceptible to impact.
The nickname “funny bone” is thought to have two possible origins. One theory links it to the humerus, the upper arm bone, through which the nerve passes; the word “humerus” sounds similar to “humorous.” Another explanation attributes the name to the “funny” or unusual tingling sensation that results when the nerve is struck. Both possibilities highlight the unique and often surprising feeling associated with hitting this unprotected nerve.
Why the Sensation?
When the ulnar nerve is struck, it undergoes temporary compression or irritation against the underlying medial epicondyle. This sudden mechanical pressure disrupts the nerve’s normal transmission of electrical signals to and from the brain.
The disruption of these signals results in the characteristic “funny” feeling. This sensation can manifest as a sharp, shooting pain, tingling, numbness, or a distinct “pins and needles” feeling that can radiate down the forearm and into the fingers. This sensation is a temporary neurological response to the nerve’s irritation, not an indication of actual bone damage from the impact.
Beyond the Elbow: The Ulnar Nerve’s Function
Beyond its role in causing a temporary jolt at the elbow, the ulnar nerve serves important functions in the everyday operation of the arm and hand. It is a major peripheral nerve that provides both motor and sensory innervation. This means it controls muscle movement and detects sensations like touch and temperature.
The ulnar nerve supplies motor signals to many of the small muscles within the hand, which are responsible for intricate and fine motor skills such as gripping, pinching, and precise finger movements. It also innervates some muscles in the forearm that contribute to wrist and finger flexion. Furthermore, it provides sensory information from the skin of the little finger and the ring finger, specifically the side closer to the little finger, as well as the corresponding parts of the palm.