A prosthetic component suitable for long-term implantation is provided. The prosthetic component includes electronic circuitry and sensors to measure a parameter of the muscular-skeletal system. The prosthetic component comprises a first structure having at least one support surface, a second structure having at least one feature configured to couple to bone. The electronic circuitry and sensors are hermetically sealed within the prosthetic component. Sensors can be used to monitor synovial fluid in proximity to the joint to determine joint health. The prosthetic component can include a temperature sensor or a pH sensor. The temperature or pH of the synovial fluid can be correlated to a variety of joint conditions. Measurements over time can be analyzed for trends. The temperature or pH can be calibrated for the patient. For example, calibration can be for temperature or pH of a patient healthy joint. The measurements are compared against this patient reference.