Carpal Bones

Description

Normal anatomy of the carpal bones. Diagram of the wrist (frontal view) shows the eight carpal bones and the three carpal arcs (Gilula arcs), which are shown as pink (arc I), blue (arc II), and red (arc III) lines. C (capitate), H (hamate), L (lunate), P (pisiform), S (scaphoid), Tm (trapezium), Td (trapezoid), Tr (triquetrum)

Wrist radiograph with carpal bones labeled

Volar view of the bony anatomy of the left wrist showing the eight carpal bones, distal radius and distal ulna individually labeled. The proximal carpal row consists of the scaphoid (S), lunate (L), and triquetrum (TQ). The distal row consists of the pisiform (P), trapezium (TP), trapezoid (TZ), and hamate (H)

Other Names

• Carpal Bones
• Carpus (plural: carpi)
• Wrist Bones
• Bones of the Wrist
• Carpus
• Carpal Bone Group
• Carpal Bone Anatomy
• Wrist Carpal Bones

General

• Group of eight irregularly shaped bones
• Organized into proximal row and distal row
• Connects the forearm to the hand

Proximal Row

• In order from radial to ulnar:
• Scaphoid, Lunate, Triquetrum, Pisiform

Distal Row

• In order from radial to ulnar:
• Trapezium, Trapezoid, Capitate, Hamate

Articulation with the Wrist Joint

• Radiocarpal Joint: scaphoid, lunate, triquetrum articulate with the radius
• Ulnocarpal Joint: lunate, triquetrum articulate with the distal ulna

Articulation with the Carpometacarpal Joints

• First: 1st metacarpal articulates with the scaphoid
• Second: 2nd metacarpal articulates trapezium, trapezoid and capitate
• Third: 3rd metacarpal articulates with capitate
• Fourth: 4th metacarpal articulates with capitate, hamate
• Fifth: 5th metacarpal articulates with hamate

Vascular Supply

• Branches of the
  • Radial Artery
  • Ulnar Artery

Innervation

• Anterior interosseous branch of the median nerve
• Posterior interosseous branch of the radial nerve
• Dorsal and the deep branches of the ulnar nerve

Biomechanics & Function

• Enable complex wrist motion (flexion, extension, deviation)
• Transmit load from hand to forearm
• Maintain stability during grip and athletic activity

Gilulas Lines

• Gilula’s lines are three smooth, continuous arcs used to assess carpal alignment
• Drawn along the proximal and distal contours of the carpal bones
• Normal finding: smooth, uninterrupted curves with no step-off
• Disruption indicates carpal instability, ligament injury, or fracture-dislocation
• Acts similarly to a “screening sign”—like a fat pad sign—indicating underlying injury

---

Radiograph demonstrating Gilula’s lines. Line I represents the proximal articular surfaces of the proximal carpal row. Line II represents the distal articular surfaces of the first carpal row. Line III represents the proximal articular surfaces of the distal carpal row. Disruption of these lines is indicative of a boney (greater arc) or ligamentous (lesser arc) injury.

Clinical Significance

Pathology

• Scaphoid Fracture
• Hamate Fracture
• Triquetrum Fracture
• Lunate Fracture
• Scapholunate Ligament Injury
• Lunotriquetral Instability
• Carpal Instability (e.g., DISI/VISI deformities)
• Lunate Dislocation
• Perilunate Dislocation
• Acute Carpal Tunnel Syndrome
• Kienböck Disease
• Preiser Disease
• Wrist Arthritis

---

See Also

• Wrist Pain (Main)
• Hand and Wrist Anatomy (Main)
• Physical Exam Wrist

---