Abstract: A dual-plane joint monitor has a pair of arms for releasable attachment to body joint members and a gimbal assembly connecting the arms for their relative rotation in two perpendicular planes. Two potentiometers generate signals indicative of an angular motion of the arms. A miniaturized electronic module, worn by a patient, is pre-programmed from a remote computer (an allowed range of motion is pre-set), reads and processes signals from the potentiometers and determines whether the allowed range of motion is exceeded. The data stored in the electronic module are transmitted periodically to the remote computer for further analysis. If needed, the physician re-programs the electronic module from the computer at a medical facility while the patient is at home, or at another remote location.