The lunate bone is a crescent-shaped carpal bone that is found in the proximal row. It is obliquely positioned in the middle of the row. Like the scaphoid bone, it also links the hand with the forearm through the articulation with the radius at the radiocarpal joint.

The dorsal surface and palmar surface of the bone are somewhat triangular-shaped and roughened (the palmar surface is larger). They are non-articular aspects of the bone, serving as attachment sites for various ligaments. The distal and proximal surfaces are covered by cartilage.

The lunate articulates with five bones - radius proximally, scaphoid laterally, capitate bone and hamate bone distally, and triquetral bone medially. Therefore, it has the following five articular surfaces:

Articular surface for radius - convex;
Articular surface for scaphoid - flat, narrow, and semilunar;
Articular surface for capitate - deeply concave;
Articular surface for hamate - appears like a curved semilunar ridge;
Articular surface for triquetral - roughly square-shaped.

The large and deeply concave surface for the capitate and the opposite convex surface for the radius give the bone its characteristic appearance. The hamate and lunate only come into direct contact when the hand is adducted.

Note: The lunate is positioned in close proximity to the median nerve. One of the injury types that occurs in young adults is lunate dislocation due to high-energy trauma. The bone displacement can result in median nerve injury and compression, presenting as entrapment neuropathy.

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Lunate