The palm bones
Metacarpal bones · ossa metacarpi
Five long bones that form the palm, one leading to each finger and thumb.
What it does
The metacarpals run from the wrist to the base of each finger. Their rounded heads form your knuckles when you make a fist. The thumb's metacarpal is short and mobile, while those of the index and middle fingers are firmly fixed, giving the hand a stable core.
Surprising fact
Breaking the neck of the fifth metacarpal is so often caused by punching a hard surface that it is nicknamed a "boxer's fracture".
Why it matters
The arched arrangement of the metacarpals lets your palm cup around objects of different sizes, from a ball to a coffee mug.
Nearby
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Sources
Drafted with AI help; awaiting a human fact-check against these sources.
Open in the 3D atlas · Suggest a correction · Not medical advice.
3D models: Z-Anatomy & BodyParts3D (CC BY-SA 4.0 / 2.1 JP). Card text CC BY 4.0.