Radius vs Ulna: Key Differences in Forearm Anatomy
Radius is the shorter, thicker forearm bone on the thumb side; Ulna is the longer, thinner one on the pinky side.
People swap the names because both bones sit close together and rotate around each other—easy to forget which is “inside” or “outside.”
Key Differences
Radius pivots at the wrist and elbow, letting your palm flip. Ulna stays stable, forming the hinge for bending and straightening.
Examples and Daily Life
Turning a doorknob or twisting a jar lid uses the Radius; resting your forearm on a desk mostly involves the Ulna.
Which bone lets my hand rotate?
The Radius allows the palm-up, palm-down motion.
Can one bone work without the other?
Both cooperate; neither alone supports full forearm movement.