The wrist-joint is a condyloid articulation. The parts forming it are the lower end of the radius and under surface of the articular disk above; and the navicular, lunate, and triangular bones below. The articular surface of the radius and the under surface of the articular disk form together a transversely elliptical concave surface, the receiving cavity. The superior articular surfaces of the navicular, lunate, and triangular form a smooth convex surface, the condyle, which is received into the concavity. The joint is surrounded by a capsule, strengthened by the following ligaments:
The Volar Radiocarpal Ligament (ligamentum radiocarpeum volare; anterior ligament) (Fig. 334).This ligament is a broad membranous band, attached above to the anterior margin of the lower end of the radius, to its styloid process, and to the front of the lower end of the ulna; its fibers pass downward and medialward to be inserted into the volar surfaces of the navicular, lunate, and triangular bones, some being continued to the capitate. In addition to this broad membrane, there is a rounded fasciculus, superficial to the rest, which reaches from the base of the styloid process of the ulna to the lunate and triangular bones. The ligament is perforated by apertures for the passage of vessels, and is in relation, in front, with the tendons of the Flexor digitorum profundus and Flexor pollicis longus; behind, it is closely adherent to the anterior border of the articular disk of the distal radioulnar articulation.
The Dorsal Radiocarpal Ligament (ligamentum radiocarpeum dorsale; posterior ligament) (Fig. 335).The dorsal radiocarpal ligament less thick and strong than the volar, is attached, above, to the posterior border of the lower end of the radius; its fibers are directed obliquely downward and medialward, and are fixed, below, to the dorsal surfaces of the navicular, lunate, and triangular, being continuous with those of the dorsal intercarpal ligaments. It is in relation, behind, with the Extensor tendons of the fingers; in front, it is blended with the articular disk.
The Ulnar Collateral Ligament (ligamentum collaterale carpi ulnare; internal lateral ligament) (Fig. 334).The ulnar collateral ligament is a rounded cord, attached above to the end of the styloid process of the ulna, and dividing below into two fasciculi, one of which is attached to the medial side of the triangular bone, the other to the pisiform and transverse carpal ligament.
The Radial Collateral Ligament (ligamentum collaterale carpi radiale; external lateral ligament) (Fig. 335).The radial collateral ligament extends from the tip of the styloid process of the radius to the radial side of the navicular, some of its fibers being prolonged to the greater multangular bone and the transverse carpal ligament. It is in relation with the radial artery, which separates the ligament from the tendons of the Abductor pollicis longus and Extensor pollicis brevis.
Synovial Membrane (Fig. 336).The synovial membrane lines the deep surfaces of the ligaments above described, extending from the margin of the lower end of the radius and articular disk above to the margins of the articular surfaces of the carpal bones below. It is loose and lax, and presents numerous folds, especially behind.