Triquetrum bone
Os triquetrum
The triquetrum is a pyramid-shaped carpal bone on the little finger side of the wrist. It lies in the proximal row, next to the lunate, and carries the pisiform on its palm surface.
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Free 3D model of the triquetrum bone. Right hand. Drag to rotate, zoom with + and − (or Ctrl + scroll), click a bone to highlight and name it.
Key points
- The triquetrum is the carpal bone on the little finger side of the proximal row.
- It joins the lunate, the hamate and the pisiform.
- It does not touch the ulna. A cartilage disc lies between them.
- It is the second most commonly fractured carpal bone, usually as a chip from its back surface.
What is the triquetrum?
The triquetrum is one of the eight carpal bones. Its name is Latin for three-cornered, and it is also called the triquetral or triangular bone.
It belongs to the proximal row, the row of wrist bones next to the forearm. It is the innermost of the three bones in that row that take part in wrist movement.
Where is the triquetrum?
It lies on the little finger side of the wrist, just beyond the head of the ulna. The lunate is beside it, the hamate is beyond it, and the pisiform rests on its palm surface.
To find it, feel for the pointed tip of the ulna on the back of your wrist, on the little finger side. Slide the finger a little further towards the hand and tilt the hand towards the thumb. The bone that becomes prominent under the finger is the triquetrum.
What does the triquetrum look like?
The bone is shaped like a small pyramid. Its base faces the lunate and its blunt tip points down and towards the little finger side.
On its palm surface is a small oval facet for the pisiform. The surface facing the hamate is gently curved, partly convex and partly concave, which lets the two bones twist on each other. The back surface is rough for ligaments.
What does the triquetrum articulate with?
The triquetrum touches three bones: the lunate on its thumb side, the hamate beyond it, and the pisiform in front of it.
It does not form a joint with the ulna. A triangular disc of cartilage sits between the head of the ulna and the triquetrum. The model shows bones only, so a gap appears where the disc would be.
What attaches to the triquetrum?
No muscles attach to the triquetrum directly. It is an anchor for ligaments, including the ulnar collateral ligament of the wrist, which runs from the tip of the ulna to the triquetrum and pisiform.
Other ligaments tie it to the lunate, the hamate and the back of the radius. The pisiform, which sits on it, carries the tendon of flexor carpi ulnaris, a muscle that bends the wrist.
What does the triquetrum do?
It supports the little finger side of the wrist. Load from the ring and little fingers passes through the hamate to the triquetrum and then across the cartilage disc to the ulna.
It also takes part in side-to-side movement. As the hand tilts towards the little finger, the triquetrum slides along the hamate and moves closer to the ulna.
Common problems with the triquetrum
The triquetrum is the second most commonly fractured carpal bone, after the scaphoid. The usual injury is a small chip pulled or knocked off its back surface in a fall on the hand. Breaks through the body of the bone are less common.
A tear of the ligament between the lunate and the triquetrum can make the little finger side of the wrist unstable and painful. This page describes anatomy only.
Common questions
Does the triquetrum touch the ulna?
No. A disc of cartilage separates them.
Why is it called the triquetrum?
The word is Latin for three-cornered, after its pyramid shape.
Which bone sits on the triquetrum?
The pisiform, on its palm surface.
Is the triquetrum the same as the triquetral bone?
Yes. Triquetrum, triquetral bone and triangular bone are all names for the same bone.
Is this 3D model of the triquetrum bone free?
Yes. The interactive 3D model on this page is free to view and use for study, with no account or download needed. Its geometry comes from the open BodyParts3D data set (CC BY-SA).
About this free 3D model of the triquetrum bone
The interactive 3D model on this page is free to use in your browser, with no sign-up. It is built from scan-based anatomy data, so every bone is a separate, correctly placed shape you can turn and inspect from any side.