The pisiform (pea bone)
Pisiform bone · os pisiforme
A pea-sized bone you can feel at the base of your palm on the little-finger side.
What it does
The pisiform is a small round bone that sits on top of the triquetrum. It lies inside the tendon of a forearm muscle, flexor carpi ulnaris, and gives that muscle extra leverage to bend the wrist. You can feel it as a hard bump at the heel of your hand.
Surprising fact
The pisiform is the last wrist bone to form, often not turning into bone until around ages nine to twelve, and its name means "pea-shaped".
Why it matters
The bump of the pisiform marks where the ulnar nerve and artery enter the hand, so leaning heavily on that spot, as cyclists do on handlebars, can leave the little finger numb.
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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.