When you bump a certain spot on your elbow, a sudden, tingling, sometimes painful sensation shoots down your arm. This common experience is known as “hitting your funny bone.” It often raises questions about what is being struck and why it elicits such a unique reaction.
It’s Not a Bone, It’s a Nerve
Despite its name, the “funny bone” is not a bone. The sensation comes from hitting the ulnar nerve, one of three main nerves in the arm. Nerves transmit electrical signals for movement and sensation throughout the body. This nerve acts as a communication pathway between your brain and parts of your forearm, hand, and fingers. The ulnar nerve enables fine motor skills, such as gripping objects, and relays sensory information like touch, temperature, and pain.
Where the Ulnar Nerve Lies
The ulnar nerve originates in the neck, travels down the arm, and extends into the hand. While much of its path is protected by muscle, fat, and bone, a specific segment at the elbow is exposed. Here, it passes through a narrow passageway called the cubital tunnel, located on the inside of the elbow.
This tunnel sits directly behind a bony protrusion of the humerus (the upper arm bone) called the medial epicondyle. The nerve’s superficial position in this area, covered by only a thin layer of skin and minimal soft tissue, makes it susceptible to impact. When the elbow is bent, the nerve can stretch and become more vulnerable to compression against this bony landmark.
Why It Feels “Funny”
When the ulnar nerve receives a direct blow, the impact temporarily disrupts its normal electrical signaling. This disturbance results in the characteristic “funny” feeling: tingling, numbness, and pain that radiates down the forearm to the ring and pinky fingers. The sensation occurs because the nerve, which controls motor and sensory input to these areas, is directly stimulated. This direct irritation differs from typical pain signals, which usually arise from tissue damage. The temporary nature of the feeling is due to the brief disruption of these signals rather than lasting damage.
Protecting Your Ulnar Nerve
While the “funny bone” sensation is generally temporary and harmless, you can take steps to protect this vulnerable nerve. Being mindful of elbow placement, especially when leaning on hard surfaces, can help prevent impacts. Ergonomic adjustments, such as proper seating height at a desk, can also reduce nerve pressure. If you experience persistent pain, numbness, or weakness in your hand or fingers, or if symptoms do not resolve quickly, seeking medical attention is advisable to rule out significant nerve irritation or compression.