Arm · Long bone
Ulna (Forearm Bone)
The ulna is one of the two forearm bones, on the little-finger side. It forms the main hinge of the elbow — the pointy part of your elbow is the top of the ulna.
What it is
The ulna runs alongside the radius on the little-finger (medial) side of the forearm. Its upper end forms the prominent point of the elbow.
Where it is
The forearm, on the little-finger side, from the elbow to the wrist.
What it does
Forms the main hinge of the elbow joint and provides stability and muscle attachment for the forearm; works with the radius to allow forearm rotation.
Connections
Joints and connections
- Elbow joint (main hinge)
- Wrist joint (small contribution)
- Joints with the radius
When things go wrong
Common injuries and conditions
- Ulnar fracture (sometimes with a radius fracture)
- Olecranon (elbow tip) fracture
Education and reference only. This explains the anatomy in plain terms; it is not a diagnosis. A severe injury, a visibly deformed limb, or the inability to move or bear weight needs urgent assessment — call 999 or go to A&E for a serious injury.
Did you know?
An interesting fact
The bony point you feel at the back of your elbow is the olecranon — the top of the ulna.
Answers
Ulna: frequently asked questions
What does the ulna do?
The ulna forms the main hinge of the elbow and stabilises the forearm, working with the radius to allow the forearm to rotate.
Which forearm bone is the ulna?
The ulna is on the little-finger (inner) side of the forearm; the radius is on the thumb side.
Explore the arm
Related bones
Sources
Where this is drawn from
- NHS — Anatomy and body systems
- Gray's Anatomy for Students (Drake, Vogl, Mitchell)
- TeachMeAnatomy — skeletal system
Building an anatomy or patient-education resource?
We create clear, accurate, referenced medical reference content and decision aids for teams.