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Portrait of Wrist joint

Anatomy · Joints & cartilage

Wrist joint

A condyloid (ellipsoid) joint

Upper limb · forearm to hand

The wrist joint proper is the radiocarpal joint, a condyloid (ellipsoid) joint between the distal radius with its articular disc above, and the scaphoid, lunate and triquetrum below. It allows flexion, extension, radial and ulnar deviation, but not rotation, which happens in the forearm. The ulna is kept out of the joint by a fibrocartilage disc.

How to spot them

  • ▸Eight small carpal bones in two rows of four, with the proximal row forming the convex surface
  • ▸The distal radius is the large bone at the joint; the head of the ulna is excluded by an articular disc
  • ▸Movement is in two planes only: bending forwards and back, and side to side
  • ▸The palmar surface carries the carpal tunnel, with the flexor retinaculum stretched across it

What to know

A condyloid joint that moves in two planes, flexion with extension and side-to-side deviation, but cannot rotate

Wrist joint — the radiocarpal joint.

Eight small bones in two rows of four lie between the forearm and the metacarpals

Wrist joint — the carpus.

A fibrocartilage disc keeps the end of the ulna out of the joint, so only the radius articulates with the carpals

Wrist joint — the triangular fibrocartilage complex.

The scaphoid is the carpal most often broken, typically in a fall on the outstretched hand

Wrist joint — scaphoid fractures risk avascular necrosis.

A fall on the outstretched hand that breaks the distal radius with dorsal displacement is named after an Irish surgeon

Wrist joint — Colles' fracture (Abraham Colles, 1814).

Key ideas

  • Two joints, one function: the radiocarpal joint plus the midcarpal joint between the carpal rows together give the wrist its range.
  • Rotation of the hand comes from the radioulnar joints in the forearm, not from the wrist itself.

Quick-fire facts

  • •The radiocarpal joint is a condyloid (ellipsoid) synovial joint: biaxial, allowing flexion, extension, adduction (ulnar deviation) and abduction (radial deviation).
  • •The carpus has eight bones: scaphoid, lunate, triquetrum, pisiform in the proximal row; trapezium, trapezoid, capitate, hamate in the distal row.
  • •The pisiform is a sesamoid bone in the tendon of flexor carpi ulnaris and takes no part in the radiocarpal joint.
  • •The scaphoid has a retrograde blood supply, so fractures of its waist can lead to avascular necrosis and non-union.
  • •Colles' fracture is a fracture of the distal radius, described by Abraham Colles in 1814.
  • •Carpal tunnel syndrome is compression of the median nerve where it crosses the wrist under the flexor retinaculum.

Drill it — 7 cards

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Sources