The little-finger-side forearm bone
Ulna · ulna
The forearm bone that forms the point of your elbow and stays still while the radius rotates.
What it does
The ulna runs from the elbow to the little-finger side of the wrist. Its hooked upper end wraps around the humerus to make the elbow hinge, and the bony point you lean on is its tip. It stays fixed while the radius rolls around it, giving the forearm a stable axis.
Surprising fact
The bony point of your elbow is the olecranon, the top of the ulna, and it is the lever your triceps pulls on to straighten your arm.
Why it matters
Leaning on your elbows presses on the ulna's tip, and a fluid-filled sac over it can swell up if you lean a lot, sometimes called "student's elbow".
Nearby
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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.