Articular capsule of radiocarpal joint

At a glance

English

Articular capsule of radiocarpal joint

Latin (TA2)

Capsula articularis articulatio radiocarpea

System

Joint

Region

Hand

Side

Paired, left and right

About the articular capsule of radiocarpal joint

The articular capsule of the radiocarpal joint surrounds the wrist joint proper, the ellipsoid joint between forearm and hand. Above it is fixed around the edge of the radial joint surface and the rim of the triangular articular disc that bridges the gap to the ulnar styloid. Below it attaches around the upper joint surfaces of the first-row carpals: scaphoid, lunate and triquetrum. The ulna itself does not touch the carpus; the disc lies between them and shuts the distal radioulnar joint off from the wrist.

The capsule is loose and has no outpouchings worth naming, which suits the wide range of the joint. It is thinnest on the back. Its inner lining of synovial membrane is lax and may form small folds that project into the joint. In many people the joint cavity communicates with the midcarpal joint, and the cavities of the intercarpal, carpometacarpal and intermetacarpal joints often join a common synovial space; a hole in the articular disc can also connect it with the distal radioulnar joint.

Its strength comes from thickened bands blended into its wall. On the front lie the strong palmar radiocarpal and palmar ulnocarpal ligaments, on the back the thinner dorsal radiocarpal ligament, and at the sides the radial and ulnar collateral ligaments of the wrist. The palmar bands are thick because the flexors are stronger than the extensors and the wrist is often loaded towards the palm.

Within this envelope the convex row of carpal bones moves in the concave socket formed by the radius and disc. The joint allows flexion and extension about a transverse axis through the capitate, and radial and ulnar deviation about a front-to-back axis. A tear of the capsule or its ligaments may follow a fall on the outstretched hand. Ganglion cysts commonly arise from the capsule on the back of the wrist, and the synovium is a frequent early site of rheumatoid arthritis, which can push the hand towards the ulnar side.

Attachments and function

Formed by

Attached above to the edge of the radial joint surface and the rim of the articular disc of the distal radioulnar joint.

Joins

Attached below to the margins of the upper surfaces of scaphoid, lunate and triquetrum.

Movements

Encloses and seals the wrist joint, holds the synovial fluid and, through its ligaments, limits excessive flexion, extension and side-to-side movement.

Nerve supply

Branches of the anterior and posterior interosseous nerves, with twigs from the ulnar and radial nerves.

Blood supply

The palmar and dorsal carpal arches, formed by branches of the radial, ulnar and interosseous arteries.