Upper limb · Hand
Carpal bones
The eight carpal bones form the skeleton of the wrist, in a proximal and a distal row of four. Together they make an arch whose palmar hollow, roofed by the flexor retinaculum, is the carpal tunnel.
- Latin (TA)
- Ossa carpi
- Type
- Short bones: eight small, roughly cuboidal bones with several articular surfaces
- Side
- Paired — right and left
- Model size
- 5.1 cm longest
Showing a right set. Rotate it to inspect every surface; switch sides to practise siding.
3D model: Z-Anatomy (CC BY-SA 4.0), derived from BodyParts3D © DBCLS (CC BY-SA 2.1 JP). Adapted by PharmaWallah. Credits & licence
Landmarks
3 of 15 marked on the modelTap a landmark to find it on the bones and read what it is.
The largest bone of the proximal row, boat-shaped and elongated.
Where: Lateral end of the proximal row; it lies in the floor of the anatomical snuffbox.
Why it matters: Articulates with the radius proximally and distally with the trapezium, trapezoid and capitate, so it links the two rows; it is the carpal bone most often fractured.
Related: Wrist joint
Viva: Which carpal bone is most commonly fractured?
A rounded projection on the palmar surface of the scaphoid.
Where: Lateral, distal part of the palmar surface; palpable at the base of the thenar eminence.
Why it matters: Lateral attachment of the flexor retinaculum (with the trapezium); gives origin to some thenar muscle fibres.
Related: Flexor retinaculum
Marked on the model at the point Z-Anatomy places this label.
The narrowed middle part of the scaphoid between its proximal and distal poles.
Where: Middle of the scaphoid.
Why it matters: The usual site of scaphoid fracture; because blood vessels enter mainly the distal part, the proximal fragment may lose its blood supply.
A crescent (half-moon) shaped bone.
Where: Middle of the proximal row, between the scaphoid and triquetrum.
Why it matters: Articulates with the radius proximally; it is the carpal bone most commonly dislocated, usually forwards into the carpal tunnel.
Related: Wrist joint
Viva: Which carpal bone is most commonly dislocated?
A pyramid-shaped bone with an oval facet on its palmar surface.
Where: Medial end of the proximal row (excluding the pisiform).
Why it matters: Articulates with the pisiform in front and, during movement, with the articular disc of the wrist.
A small, pea-shaped sesamoid bone.
Where: On the palmar surface of the triquetrum; palpable at the medial end of the distal wrist crease.
Why it matters: Lies in the tendon of flexor carpi ulnaris; medial attachment of the flexor retinaculum; origin of abductor digiti minimi.
Related: Flexor carpi ulnaris; flexor retinaculum
Viva: Which carpal bone is a sesamoid bone?
An irregular four-sided bone at the lateral end of the distal row.
Where: Lateral end of the distal row, at the base of the thumb.
Why it matters: Forms the carpometacarpal joint of the thumb with the first metacarpal.
Related: Carpometacarpal joint of thumb
An articular surface concave in one direction and convex in the other.
Where: Distal surface of the trapezium.
Why it matters: Makes the first carpometacarpal joint a saddle joint, which allows opposition of the thumb.
Related: Carpometacarpal joint of thumb
A ridge-like projection on the palmar surface of the trapezium.
Where: Palmar surface of the trapezium.
Why it matters: Lateral attachment of the flexor retinaculum; gives origin to thenar muscle fibres.
Related: Flexor retinaculum
Marked on the model at the point Z-Anatomy places this label.
A small, wedge-shaped bone.
Where: Distal row, between the trapezium and capitate.
Why it matters: Articulates distally with the base of the second metacarpal.
The largest carpal bone, with a rounded head.
Where: Centre of the distal row.
Why it matters: Its head fits into the concavity formed by the scaphoid and lunate; distally it articulates mainly with the third metacarpal.
Viva: Which is the largest carpal bone?
A wedge-shaped bone with a hook on its palmar surface.
Where: Medial end of the distal row.
Why it matters: Articulates distally with the fourth and fifth metacarpals.
A curved, hook-like process projecting forwards from the palmar surface of the hamate.
Where: Distal part of the palmar surface of the hamate; felt deep in the hypothenar eminence.
Why it matters: Medial attachment of the flexor retinaculum; forms the lateral boundary of the ulnar canal (Guyon's canal), with the pisiform medially; gives origin to hypothenar muscles.
Related: Flexor retinaculum; ulnar canal
Viva: What passes between the pisiform and the hook of the hamate?
Marked on the model at the point Z-Anatomy places this label.
The hollow on the palmar side of the articulated carpus.
Where: Palmar surface of the carpus, between the scaphoid and trapezium tubercles laterally and the pisiform and hook of hamate medially.
Why it matters: Converted into the carpal tunnel by the flexor retinaculum; the median nerve and the long flexor tendons pass through it.
Related: Carpal tunnel
Classification & region
Short bones: eight small, roughly cuboidal bones with several articular surfaces; the pisiform is also a sesamoid bone, lying in the tendon of flexor carpi ulnaris.
- Scaphoid
- Proximal row, lateral. Boat-shaped; has a tubercle on its palmar surface; articulates with the radius.
- Lunate
- Proximal row, between scaphoid and triquetrum. Half-moon (crescent) shaped; articulates with the radius.
- Triquetrum
- Proximal row, medial. Pyramid-shaped; has an oval facet on its palmar surface for the pisiform.
- Pisiform
- Small pea-shaped sesamoid bone on the palmar surface of the triquetrum, in the tendon of flexor carpi ulnaris.
- Trapezium
- Distal row, lateral. Has a saddle-shaped facet for the first metacarpal and a palmar tubercle with a groove medial to it.
- Trapezoid
- Distal row, between trapezium and capitate. Small and wedge-shaped; articulates with the second metacarpal.
- Capitate
- Distal row, centre. The largest carpal bone, with a rounded head that fits into the hollow formed by the scaphoid and lunate.
- Hamate
- Distal row, medial. Wedge-shaped, with a hook projecting from its palmar surface; articulates with the fourth and fifth metacarpals.
Hold it in the anatomical position
- In the articulated hand, read the proximal row from lateral (thumb side) to medial: scaphoid, lunate, triquetrum, pisiform.
- Then the distal row from lateral to medial: trapezium, trapezoid, capitate, hamate.
- The palmar surface of the carpus is concave from side to side (the carpal groove); the dorsal surface is convex.
- The four palmar projections are the scaphoid and trapezium tubercles laterally, and the pisiform and the hook of the hamate medially.
Right or left? Side determination
- Articulated set: put the concave palmar surface forwards and the proximal row (with the convex scaphoid–lunate surface for the radius) upwards. The side with the trapezium's saddle facet for the thumb is lateral.
- Hamate (the most reliable single bone): the hook is on the palmar surface, the two facets for the fourth and fifth metacarpals are distal, and the concave face of the hook looks laterally towards the carpal tunnel. With these fixed, the bone belongs to the hand whose thumb side the concavity of the hook faces.
- Trapezium: the saddle-shaped facet for the first metacarpal is distal and the tubercle is palmar, with the groove for flexor carpi radialis on the medial side of the tubercle.
- Scaphoid: the large convex facet for the radius faces proximally, the tubercle is palmar and distal, and the concave facet for the capitate faces medially.
- Be honest in the viva: siding an isolated lunate, triquetrum, trapezoid or pisiform is difficult and is not usually expected; examiners normally ask you to name it and say which surfaces articulate with what.
Check yourself: switch the 3D model to “Left bone” and apply the same steps.
Articulations
- With the radius at the Wrist (radiocarpal) joint — Proximal surfaces of the scaphoid and lunate (the triquetrum meets the articular disc)..
- With the each other at the Intercarpal and midcarpal joints — Facets between neighbouring carpal bones; the midcarpal joint lies between the two rows..
- With the pisiform with triquetrum at the Pisotriquetral joint — Facet on the palmar surface of the triquetrum and the dorsal facet of the pisiform..
- With the metacarpals at the Carpometacarpal joints — Distal row: trapezium (first and second metacarpals), trapezoid (second), capitate (mainly third), hamate (fourth and fifth)..
Muscle and ligament attachments
| Structure | Type | Where on the bone |
|---|---|---|
| Flexor carpi ulnaris | insertion | Pisiform (continued to the hook of hamate and fifth metacarpal by the pisohamate and pisometacarpal ligaments). |
| Flexor retinaculum | ligament | Medially the pisiform and hook of hamate; laterally the tubercles of the scaphoid and trapezium. |
| Abductor digiti minimi | origin | Pisiform. |
| Flexor digiti minimi brevis and opponens digiti minimi | origin | Hook of hamate and flexor retinaculum. |
| Thenar muscles (abductor pollicis brevis, flexor pollicis brevis, opponens pollicis) | origin | Flexor retinaculum and the tubercles of the scaphoid and trapezium. |
| Adductor pollicis (oblique head) | origin | Capitate and the bases of the second and third metacarpals. |
| Palmar and dorsal radiocarpal and intercarpal ligaments | ligament | Palmar and dorsal surfaces of the carpal bones. |
Functions
- Form a flexible link between the forearm and the hand, allowing wrist movement.
- Transmit force from the hand to the radius.
- Form the bony floor and walls of the carpal tunnel.
- Give attachment to the flexor retinaculum and the thenar and hypothenar muscles.
Clinical & practical relevance
- Scaphoid fracture: the commonest carpal fracture, usually from a fall on the outstretched hand; it causes tenderness in the anatomical snuffbox. It is easily missed on early X-rays.
- Because blood vessels enter the scaphoid mainly at its distal part, a fracture through the waist can deprive the proximal fragment of blood, leading to non-union or avascular necrosis.
- Lunate dislocation: the lunate is the carpal bone most often dislocated, usually forwards, where it can compress the median nerve in the carpal tunnel. Avascular necrosis of the lunate is known as Kienböck's disease.
- Carpal tunnel syndrome: compression of the median nerve in the carpal tunnel causes tingling and weakness in its distribution in the hand.
- Fracture of the hook of the hamate (for example in golf or racquet sports) can injure the nearby ulnar nerve or artery.
Identification tips
- A common mnemonic: "Some Lovers Try Positions That They Can't Handle" (scaphoid, lunate, triquetrum, pisiform; trapezium, trapezoid, capitate, hamate).
- Trapezium is under the thumb ("the trapeziUM is by the thUMb"); the trapezoid is next to it.
- The hamate is the easiest bone to recognise by its hook; the capitate by its size and rounded head; the pisiform by its pea shape and single facet.
- Four palmar landmarks anchor the flexor retinaculum: two lateral (scaphoid and trapezium tubercles), two medial (pisiform, hook of hamate).
Common student mistakes
- Mixing up the trapezium and trapezoid.
- Saying the triquetrum articulates directly with the ulna: the ulna is separated from the carpus by the articular disc.
- Listing the pisiform in the distal row; it belongs to the proximal row.
- Claiming that every isolated carpal bone can be sided reliably. It cannot; say so and name its articulations instead.
Common exam questions
Name the carpal bones in order.Show answer
Proximal row, lateral to medial: scaphoid, lunate, triquetrum, pisiform. Distal row, lateral to medial: trapezium, trapezoid, capitate, hamate.
Which carpal bones articulate with the radius?Show answer
The scaphoid and the lunate.
Which carpal bone is most commonly fractured, and why is the fracture troublesome?Show answer
The scaphoid; its proximal part can lose its blood supply, giving non-union or avascular necrosis.
What are the attachments of the flexor retinaculum?Show answer
Medially the pisiform and the hook of the hamate; laterally the tubercles of the scaphoid and trapezium.
Which carpal bone is a sesamoid?Show answer
The pisiform, in the tendon of flexor carpi ulnaris.
How would you side a hamate?Show answer
Hook palmar, metacarpal facets distal; the hook's concave face looks laterally, towards the carpal tunnel.
Which is the largest carpal bone?Show answer
The capitate.
What forms the carpometacarpal joint of the thumb?Show answer
The saddle-shaped facet of the trapezium with the base of the first metacarpal.
Revision summary
- Eight short bones in two rows of four.
- Proximal (lateral→medial): scaphoid, lunate, triquetrum, pisiform.
- Distal (lateral→medial): trapezium, trapezoid, capitate, hamate.
- Radius meets scaphoid and lunate.
- Flexor retinaculum: pisiform + hook of hamate; scaphoid + trapezium tubercles.
- Scaphoid: commonest fracture, snuffbox tenderness, proximal-pole avascular necrosis.
- Lunate: commonest dislocation; median nerve at risk.
- Pisiform: sesamoid in flexor carpi ulnaris.
Test yourself on the carpal bones
Spotting questions on bones, sides and landmarks — untimed, with explanations.
Joints of the carpal bones
References
- Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. 5th ed. Philadelphia: Elsevier; 2023.
- Moore KL, Dalley AF, Agur AMR. Moore's Clinically Oriented Anatomy. 9th ed. Philadelphia: Wolters Kluwer; 2023.
- Federative International Programme for Anatomical Terminology (FIPAT). Terminologia Anatomica. 2nd ed. FIPAT.library.dal.ca; 2019. fipat.library.dal.ca/TA2
- Kervyn G, Zielinski M, Vinent L, et al. Z-Anatomy: the libre 3D atlas of anatomy. Models derived from BodyParts3D, The Database Center for Life Science (CC BY-SA 2.1 JP). CC BY-SA 4.0. www.z-anatomy.com/
Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy