It is situated in the center of the proximal row carpal bones, which lie between the ulna and radius and the hand.

The lateral surface is flat and narrow, with a crescentic facet for articulation with the scaphoid bone.

The medial surface possesses a smooth and quadrilateral facet for articulation with the triquetral bone.

In amphibians and reptiles, the bone is instead referred to as the intermedium, because of its position between the other two proximal carpals.

This article incorporates text in the public domain from page 224 of the 20th edition of Gray's Anatomy (1918)