Triquetral bone bone fragment on lateral views. The etymology derives from the Latin "triquetrus" which means "three-cornered." Therefore, it is sometimes also called the triangular bone or os triangulare. However, "os triangulare" may also refer to a nearby accessory bone. Triquetral bone The triquetral bone (; also called triquetrum, pyramidal, three-faced, and formerly cuneiform bone) is located in the wrist on the medial side of the proximal row of the carpus between the lunate and pisiform bones. It is on the ulnar side of the hand, but does not articulate with the ulna. It connects with the pisiform, hamate, and lunate bones.
Carpal bones or "distal surfaces" are articular, the superior generally convex, the inferior concave; the "medial" and "lateral surfaces" are also articular where they are in contact with contiguous bones, otherwise they are rough and tuberculated. The structure in all is similar: cancellous tissue enclosed in a layer of compact bone. Occasionally accessory bones are found in the carpus, but of more than 20 such described bones, only four (the central, styloid, secondary trapezoid, and secondary pisiform bones) are considered to be proven accessory bones. Sometimes the scaphoid, triquetrum, and pisiform bones are divided into two. The carpal bones are ossified endochondrally