Second metacarpal bone

The second metacarpal bone (metacarpal bone of the index finger) is the longest, and its base the largest, after the first metacarpal.

Its base is prolonged upward and medialward, forming a prominent ridge.

It presents four articular facets: three on the upper surface and one on the ulnar side.

Of the facets on the upper surface:
 * the intermediate is the largest and is concave from side to side, convex from before backward for articulation with the lesser multangular;
 * the lateral is small, flat and oval for articulation with the greater multangular;
 * the medial, on the summit of the ridge, is long and narrow for articulation with the capitate.

The facet on the ulnar side articulates with the third metacarpal.

The extensor carpi radialis longus muscle is inserted on the dorsal surface and the flexor carpi radialis muscle on the volar surface of the base.