Bones of hand

The skeleton of the human hand consists of 27 bones:

the eight short carpal bones of the wrist are organized into a proximal row (scaphoid, lunate, triquetral and pisiform) which articulates with the bones of the forearm, and a distal row (trapezium, trapezoid, capitate and hamate), which articulates with the bases of the five metacarpal bones of the hand.

The heads of the metacarpals will each in turn articulate with the bases of the proximal phalanx of the fingers and thumb.

These articulations with the fingers are the metacarpophalangeal joints known as the knuckles.

At the palmar aspect of the first metacarpophalangeal joints are small, almost spherical bones called the sesamoid bones.

The fourteen phalanges make up the fingers and thumb, and are numbered I-V (thumb to little finger) when the hand is viewed from an anatomical position (palm up).

The four fingers each consist of three phalanx bones: proximal, middle, and distal.

The thumb only consists of a proximal and distal phalanx.

Together with the phalanges of the fingers and thumb these metacarpal bones form five rays or poly-articulated chains.

Because supination and pronation (rotation about the axis of the forearm) are added to the two axes of movements of the wrist, the ulna and radius are sometimes considered part of the skeleton of the hand.

There are numerous sesamoid bones in the hand, small ossified nodes embedded in tendons; the exact number varies between people:

whereas a pair of sesamoid bones are found at virtually all thumb metacarpophalangeal joints, sesamoid bones are also common at the interphalangeal joint of the thumb (72.9%) and at the metacarpophalangeal joints of the little finger (82.5%) and the index finger (48%).