At least one embodiment is directed to an insert for measuring a parameter of the muscular-skeletal system. The insert can be temporary or permanent. In one embodiment, the insert is prosthetic component for a single compartment of the knee. The insert comprises a support structure and a support structure respectively having an articular surface and a load bearing surface. The height of the insert is less than 10 millimeters. At least one internal cavity is formed when support structures are coupled together for housing electronic circuitry, sensors, and the power source. The cavity can be sterilized through a port. A membrane is between the port and the cavity. A sterilization gas permeates the membrane for sterilizing cavity. The membrane reduces the ingress of solids and liquids to the cavity.