The present invention adopts Active Sensing and Passive Sensing methods to monitor the health of artificial joints through detection of impaired function in the form ofboundary lubrication, fretting and abrasion, and impingement of non-articulating surfaces. A piezoelectric transducer is mounted in the femur ball as an actuator and a second piezoelectric transducer is mounted on the exterior edge of the acetabulum socket as a sensor. When the Active sensing method is used, the actuator generates a wave which propagates from the ball to the socket; the sensor picks up the signal transmitted across the ball-socket interface, and information within the signal is correlated with changes in the frictional conditions at the articulating interface and at other areas of contact between the articulating components. In Passive sensing, a sensor mounted on one ofthe prosthetic components detects the acoustic and ultrasonic waves generated during function of the artificial joint. Features within these waves are used to detect conditions within the joint compromising its function and long-term durability.