Abstract: An apparatus and a method for monitoring the activity of a patient comprehend the sensing of the downwardly directed angular inclination of the distal end of the patient's femur to determine when the patient is in an ambulatory enabling position. The electrodes of a mercury switch, which is included in an alarm module that is attached to the patient's thigh, close to produce an electric signal whenever such inclination exceeds a preselected threshold angle. Such signal activates an alarm-generating electrical circuit to produce an alarm with a distinctive sound to provide notice to attending personnel of the possibility of impending injury to the patient.