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, and at least one sensor. The electronic circuitry and sensors are hermetically sealed within the prosthetic component. The prosthetic component includes at least on transmissive region. The transmissive region can be located in a region that has exposure to a region outside the joint. The transmissive region can comprise glass. One or more sensors can be used to monitor synovial fluid in proximity to the joint to determine joint health. The transmissive region can be used to support communication between the electronic circuitry and remote system.