Implantable sensors for determining bone health are described that can be utilized in conjunction with orthopedic implants. The sensors can include passive strain gauges or passive chemical sensors that can be read by radiographic imaging techniques. Sensors can be affixed to implantable support devices so as to non-invasively monitor the effect of load on the implant for instance to provide a quantitative assessment of when a fracture is sufficiently healed to allow safe weight-bearing upon the limb. Alternatively, sensors can monitor the health of a local implant area, for instance to monitor the implant area of early stage infection or healing of a fusion procedure.