anatomy/radius-and-ulna·Bone
Radius and ulna
Ulna et Radius
The two forearm bones. The radius rotates around the ulna, letting you turn the palm up or down.
// Structure & location
According to OpenStax, the ulna lies on the little-finger side and the radius on the thumb side. At the top, the ulna forms the point of the elbow with its hook (olecranon). The radius is narrow at the top and wide at the bottom. Only the radius forms the wrist joint with the carpal bones; the ulna doesn't.
// Function
When the forearm rotates, the radius crosses over the ulna. Palm down is called pronation, palm up supination. At the elbow both form a hinge joint with the humerus.
// For training & sport
- In bench press and push-ups the forearms should be vertical under the load so the force runs straight through the bones.
- Severe wrist pain in front squats is often due to limited mobility. A wider grip or a cross-arm grip helps.
// Good to know
People who fall and catch themselves with the hand often break the lower end of the radius just above the wrist.
// Sources
last reviewed: 2026-11-14