The lunate (semilunar bone) is one of the eight carpal bones. It lies between the scaphoid laterally and the triquetral medially. It articulates with the distal radius and triangular articular cartilage at the wrist, and the hamate and capitate distally across the midcarpal joint.
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The lunate can be felt between the dorsal tubercle of the radius and the capitate. It is most prominent at the apex of the dorsum of the hand when the wrist is flexed. A small amount of movement when grasped is normal.
The lunate is approximally semilunar in shape, hence its name. It has several surfaces - the rough triangular palmar surface, the thinner rough dorsal surface, a smooth convex proximal surface, the deeply concave distal surface, the narrow lateral surface and the square medial surface. The lateral surface has a flat semilunar facet for articulation with the scaphoid. The medial surface is separated from the distal surface by a prominent ridge, usually concave, which may articulate with the hamate in adduction.
- Articulates with the distal radius and triangular articular disc at the wrist
- Articulates with the scaphoid and triquetral at the intercarpal joints
- Articulates with the head of capitate distally
- May articulate with the edge of hamate whilst in adduction
Ossifies in the fourth year.