A system for monitoring the ambient conditions of a mammalian joint, and particularly a joint that has been instrumented with a joint endoprosthesis (10) includes a sensor (30) supported by a component (14) of the joint endoprosthesis (10). The system includes a transmission element (35) that is also supported within the body of the patient, preferably within the endoprosthesis (10). The transmission element (35) transmits a signal indicative of the sensed ambient condition within the instrumented joint. For example, the sensor (30) can be a temperature sensor used to evaluate the temperature within a joint, such as a hip joint, during activity or exercise by the patient.
