Intercarpal articulations

Intercarpal Articulations (Articulations of the Carpus) - These articulations may be subdivided into three sets:


 * 1. The Articulations of the Proximal Row of Carpal Bones.
 * 2. The Articulations of the Distal Row of Carpal Bones.
 * 3. The Articulations of the Two Rows with each Other.

Articulations of the Proximal Row of Carpal Bones
These are arthrodial. joints The navicular, lunate, and triangular are connected by dorsal, volar, and interosseous ligaments. The Dorsal Ligaments (ligamenta intercarpea dorsalia).—The dorsal ligaments, two in number, are placed transversely behind the bones of the first row; they connect the navicular and lunate, and the lunate and triangular. The Volar ligaments (ligamenta intercarpea volaria; palmar ligaments).—The volar ligaments, also two, connect the navicular and lunate, and the lunate and triangular; they are less strong than the dorsal, and placed very deeply behind the Flexor tendons and the volar radiocarpal ligament. The Interosseous Ligaments (ligamenta intercarpea interossea).—The interosseous ligaments are two narrow bundles, one connecting the lunate with the navicular, the other joining it to the triangular. They are on a level with the superior surfaces of these bones, and their upper surfaces are smooth, and form part of the convex articular surface of the wrist-joint.

The ligaments connecting the pisiform bone are the articular capsule and the two volar ligaments.

The articular capsule is a thin membrane which connects the pisiform to the triangular; it is lined by synovial membrane.

The two volar ligaments are strong fibrous bands; one, the pisohamate ligament, connects the pisiform to the hamate, the other, the pisometacarpal ligament, joins the pisiform to the base of the fifth metacarpal bone. These ligaments are, in reality, prolongations of the tendon of the Flexor carpi ulnaris.

Articulations of the Distal Row of Carpal Bones
These also are arthrodial joints; the bones are connected by dorsal, volar, and interosseous ligaments. The Dorsal Ligaments (ligamenta intercarpea dorsalia).—The dorsal ligaments, three in number, extend transversely from one bone to another on the dorsal surface, connecting the greater with the lesser multangular, the lesser multangular with the capitate, and the capitate with the hamate. The Volar Ligaments (ligamenta intercarpea volaria; palmar ligaments).—The volar ligaments, also three, have a similar arrangement on the volar surface. The Interosseous Ligaments (ligamenta intercarpea interossea).—The three interosseous ligaments are much thicker than those of the first row; one is placed between the capitate and the hamate, a second between the capitate and the lesser multangular, and a third between the greater and lesser multangulars. The first is much the strongest, and the third is sometimes wanting.

Articulations of the Two Rows of Carpal Bones with Each Other

 * See Midcarpal joint

Synovial Membrane
The synovial membrane of the carpus is very extensive, and bounds a synovial cavity of very irregular shape.

The upper portion of the cavity intervenes between the under surfaces of the navicular, lunate, and triangular bones and the upper surfaces of the bones of the second row.

It sends two prolongations upward—between the navicular and lunate, and the lunate and triangular—and three prolongations downward between the four bones of the second row.

The prolongation between the greater and lesser multangulars, or that between the lesser multangular and capitate, is, owing to the absence of the interosseous ligament, often continuous with the cavity of the carpometacarpal joints, sometimes of the second, third, fourth, and fifth metacarpal bones, sometimes of the second and third only.

In the latter condition the joint between the hamate and the fourth and fifth metacarpal bones has a separate synovial membrane.

The synovial cavities of these joints are prolonged for a short distance between the bases of the metacarpal bones.

There is a separate synovial membrane between the pisiform and triangular.

Movements
The articulation of the hand and wrist considered as a whole involves four articular surfaces:
 * (a) the inferior surfaces of the radius and articular disk;
 * (b) the superior surfaces of the navicular, lunate, and triangular, the pisiform having no essential part in the movement of the hand;
 * (c) the S-shaped surface formed by the inferior surfaces of the navicular, lunate, and triangular;
 * (d) the reciprocal surface formed by the upper surfaces of the bones of the second row.

These four surfaces form two joints: (1) a proximal, the wrist-joint proper; and (2) a distal, the mid-carpal joint.

The wrist-joint proper
The wrist-joint proper is a true condyloid articulation, and therefore all movements but rotation are permitted.

Flexion and extension are the most free, and of these a greater amount of extension than of flexion is permitted, since the articulating surfaces extend farther on the dorsal than on the volar surfaces of the carpal bones.

In this movement the carpal bones rotate on a transverse axis drawn between the tips of the styloid processes of the radius and ulna.

A certain amount of adduction (or ulnar flexion) and abduction (or radial flexion) is also permitted.

The former is considerably greater in extent than the latter on account of the shortness of the styloid process of the ulna, abduction being soon limited by the contact of the styloid process of the radius with the greater multangular.

In this movement the carpus revolves upon an antero-posterior axis drawn through the center of the wrist.

Finally, circumduction is permitted by the combined and consecutive movements of adduction, extension, abduction, and flexion.

No rotation is possible, but the effect of rotation is obtained by the pronation and supination of the radius on the ulna.

The movement of flexion is performed by the Flexor carpi radialis, the Flexor carpi ulnaris, and the Palmaris longus; extension by the Extensores carpi radiales longus and brevis and the Extensor carpi ulnaris; adduction (ulnar flexion) by the Flexor carpi ulnaris and the Extensor carpi ulnaris; and abduction (radial flexion) by the Abductor pollicis longus, the Extensors of the thumb, and the Extensores carpi radiales longus and brevis and the Flexor carpi radialis.

When the fingers are extended, flexion of the wrist is performed by the Flexor carpi radialis and ulnaris and extension is aided by the Extensor digitorum communis.

When the fingers are flexed, flexion of the wrist is aided by the Flexores digitorum sublimis and profundus, and extension is performed by the Extensores carpi radiales and ulnaris.

mid-carpal joint

 * See Midcarpal joint