Wrist joint

Articulatio radiocarpalis

Also known as: radiocarpal joint, wrist, midcarpal joint

The condyloid (ellipsoid) synovial joint between the distal radius and articular disc above and the scaphoid, lunate and triquetrum below. With the midcarpal joint it allows flexion, extension, abduction, adduction and circumduction of the hand.

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Overview

TypeCondyloid (ellipsoid) synovial, biaxial

Ulnar vs radial deviation≈30–45° vs ≈15–20°

The concave proximal surface is formed by the distal radius (scaphoid and lunate facets) and the articular disc of the triangular fibrocartilage complex over the ulnar head; the ulna does not take part directly. The convex distal surface is formed by the proximal carpal row — scaphoid, lunate and triquetrum — bound together by interosseous ligaments. In the neutral position only the scaphoid and lunate contact the radius; the triquetrum meets the disc during ulnar deviation.

The capsule is reinforced by strong palmar radiocarpal (radioscaphocapitate, long and short radiolunate) and ulnocarpal ligaments, a weaker dorsal radiocarpal ligament, and radial and ulnar collateral ligaments of the wrist. The midcarpal joint between the proximal and distal rows contributes a large share of the total movement, the two joints acting together: flexion ≈80°, extension ≈70°, adduction (ulnar deviation) ≈30–45° — greater than abduction (radial deviation) ≈15–20°, which is limited by the radial styloid.

Location: Between the forearm and the hand.

Parts & subdivisions

Proximal surface
Distal radius + articular disc of the TFCC.
Distal surface
Scaphoid, lunate and triquetrum.
Midcarpal joint
Between the proximal and distal carpal rows.
Palmar radiocarpal ligaments
Strongest stabilisers.
Collateral ligaments
Radial (styloid → scaphoid) and ulnar (styloid → triquetrum/pisiform).

Anatomy

Innervation: Anterior interosseous (median), posterior interosseous (radial), and dorsal and deep branches of the ulnar nerve.
Arterial supply: Dorsal and palmar carpal arches (radial, ulnar and anterior/posterior interosseous arteries).
Articulations: Radius and articular disc ↔ scaphoid, lunate, triquetrum.
Ligaments: Palmar and dorsal radiocarpal, ulnocarpal, radial and ulnar collateral ligaments of the wrist; intercarpal (scapholunate, lunotriquetral) ligaments.

Function

Positions the hand for grip and fine manipulation
Flexion, extension, radial and ulnar deviation, circumduction
Transmits load from the hand to the forearm

Clinical significance

FOOSH injuries

A fall on the outstretched hand may produce, by age: distal radial physeal (Salter–Harris II) or buckle fractures in children, scaphoid fractures in young adults, and Colles fractures in older adults; perilunate dislocations with high energy.

Ganglion cyst

The commonest soft-tissue swelling of the hand: a mucin-filled cyst arising from the wrist joint capsule or tendon sheath, most often dorsally over the scapholunate ligament.

Rheumatoid wrist

Synovitis destroys the TFCC and ligaments, causing radial deviation of the wrist with ulnar deviation of the fingers and dorsal prominence of the ulnar head ("caput ulnae") risking extensor tendon rupture.

Test yourself

A mid-shaft fracture of the humerus is most likely to injure which nerve, producing which sign?

Axillary nerve — loss of shoulder abduction
Ulnar nerve — claw hand
Median nerve — ape hand
Radial nerve — wrist drop

Answer: Radial nerve — wrist drop

The radial nerve lies in the radial (spiral) groove on the posterior shaft. Injury there paralyses the wrist and finger extensors (wrist drop) with sensory loss over the dorsal first web space; triceps is usually spared.

An elderly woman falls on her outstretched hand and has a "dinner-fork" deformity of the wrist. What is the fracture?

Colles fracture — dorsal displacement and angulation of the distal radius
Smith fracture — volar displacement of the distal radius
Barton fracture — intra-articular rim fracture with carpal dislocation
Galeazzi fracture — radial shaft fracture with DRUJ dislocation

Answer: Colles fracture — dorsal displacement and angulation of the distal radius

Colles fracture is a distal radial fracture with dorsal displacement and angulation, radial shortening and often ulnar styloid avulsion, typically in osteoporotic women after a FOOSH. Smith fracture is the reverse (volar displacement).