Child's hand. Coloured X-ray of the normal hand of a 10 year old. The eight wrist (carpus) bones, known collectively as the carpal bones, are still developing. The carpel bones articulate with the bones of the forearm, the ulna (bottom left) and radius (bottom right), to form the wrist joint. From the carpel bones the five metacarpals extend through the palm and join to the phalanges, the finger bones.