Abstract: An implantable self-powered sensing system for a bone fixation device, which includes a self-powered strain sensor mountable on or in a bone fixation device, is disclosed. The sensor is capable of measuring strain in the bone fixation device by generating a strain signal in response to stresses produced thereupon. The system also includes a telemetry unit powered by the generated strain signal and in communication with the sensor. The telemetry unit is activated by the sensor when the strain signal reaches a predetermined value and then transmits the strain signal from the sensor to an external receiver. The sensing system can also include a buffer unit in communication with the sensor and the telemetry unit for collecting and storing the strain signals for transmission by the telemetry unit as a cumulative strain measurement.