A system is described for sensing the relative angular orientation of two relatively movable joint segments of a living body joined together at a joint. The system comprises at least two links coupled together about a pivot axis so that the links are pivotable relative to one another about the axis so as to define a variable mechanical angle between the links about the axis. The two links are secured respectively to the joint segments so that the links pivot about the pivot axis when the joint segments pivot about said joint. A Hall effect sensor is used to accurate sense the mechanical angle. The mechanical angle sensed by the sensor is then correlated with the actual angle made by the joint segments. The arrangement is used with each finger and thumb joint of the hand to provide data representative of finger and thumb orientations of a hand.