[Fig. 53].—Elbow-joint, Lateral View.

Fig. 52.—1, humerus; 2, ulna; 3, radius. a and b, the two medial collateral ligaments.

Fig. 53.—1, humerus; 2, radius; 3, ulna. a, dorsal collateral ligament; b, ventral collateral ligament; c, annular ligament.

Closely connected with the capsule of the joint are the collateral ligaments. The two medial collateral ligaments ([Fig. 52]) arise from the medial epicondyle. One (b) passes distad and laterad to the interval between the radius and ulna; here it divides, one branch going to the head of the radius, while the other is attached to the lateral surface of the ulna at the edge of the semilunar notch. The second medial ligament (a) lies dorsad of the first; it passes to the medial surface of the ulna, at the distal edge of the semilunar notch.

The two collateral ligaments on the lateral side ([Fig. 53]) arise from the lateral epicondyle. The ventral one (b) passes almost directly distad and is inserted into the lateral surface of the proximal end of the radius about one centimeter from the articular surface; its inner surface is partly united to the annular ligament (c) of the radius. The dorsal one (a) is attached to the lateral border of the semilunar notch of the ulna.

Articulations of Radius and Ulna.—The proximal radio-ulnar articulation ([Fig. 53]) is by a pivot-joint or trochoid. The two bones are held in place by the annular ligament ([Fig. 53], c). This is attached on the lateral side to the dorsal border of the radial notch of the ulna, passes around the head of the radius, receiving some ligamentous fibres which come from the lateral epicondyle, and is attached to the coronoid process of the ulna. The annular ligament is closely united with the capsule of the joint.

The radius and ulna are united for about their middle third by the thin interosseous membrane, which fills the interosseous space between their adjacent edges.

The Wrist.—At the wrist or carpus there are in reality three joints, the first between the radius and ulna proximad and the first row of carpals distad, the second between the two rows of carpal bones, the third between the distal row of carpals and the metacarpals. The first two are movable joints; the third is not. Each of these three joints has a capsule, and the bones entering into the joints are interconnected by numerous ligaments. These ligaments are named by combining the names of the two bones which they interconnect. Ligaments which interconnect bones of the same row in the carpus are sometimes distinguished as interosseous ligaments, as contrasted with intercarpal ligaments, which connect together bones of different rows. According to their position the ligaments may also be distinguished as dorsal, ventral, and lateral. Detailed descriptions and figures of all these ligaments are given by Strauss-Durckheim.

Metacarpals.—The joint between the carpals and metacarpals has been [described]. At the distal end of the metacarpals the articulations with the phalanges have each a capsule. The joint is further strengthened by a double lateral ligament on each side. The two sesamoid bones at each joint are interconnected by a strong transverse ligament, and each is connected with the head of the metacarpal and the base of the first phalanx by a lateral ligament.