Sixteen healthy subjects were recruited for this study. A three-dimensional motion analysis system was used, with 14 retroreflective markers attached to each subject's thumb for motion data collection. Three joints including interphalangeal joint, metacarpophalangeal joint and carpometacarpal joint of the thumb were analyzed. The distal segment orientation relative to the proximal segment was defined the joint angle. The styloid process of radial bone orientation when quantifying the carpometacarpal joint movement was indirectly calculated from the third metacarpal bone