Wrist the hand: In the hand proper a total of 13 bones form part of the wrist: eight carpal bones—scaphoid, lunate, triquetral, pisiform, trapezium, trapezoid, capitate, and hamate— and five metacarpal bones—the first, second, third, fourth, and fifth metacarpal bones. The midcarpal joint is the S-shaped joint space separating the proximal and distal rows of carpal bones. The intercarpal joints, between the bones of each row, are strengthened by the radiate carpal and pisohamate ligaments and the palmar, interosseous, and dorsal intercarpal ligaments. Some degree of mobility is possible between the bones of the proximal row while the bones of the
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