The Forearm Twins
Radius and ulna â the bones that spin your hand
Your forearm has TWO bones side by side: the radius and the ulna. And here's the magic â when you turn your hand over, one bone rolls right over the other like a drumstick trick!
Radius and ulna, palm up and palm down
Real anatomy picture coming soon
Real anatomy photo spot: the radius crossing over the ulna during pronation
The twins
The ulna is the inner twin â it forms the main hinge of your elbow with the humerus. The radius is the outer twin â it's the one that carries most of the load at your wrist. They run side by side, joined by a stretchy sheet of tissue.
The spin trick
Turn your palm up (this is called supination) â the two bones lie parallel. Now turn your palm down (pronation) â the radius rolls over and across the ulna, twisting your hand like a doorknob. Try it slowly and watch your forearm twist. Two bones = one spinning hand!
Mr. Bones says: I'm a fictional skeleton, not a doctor! This is for learning and fun. If anything hurts, stop and tell a grown-up you trust.
