In-vivo measurement of tibiofemoral forces transmitted through Total Knee Replacement (TKR) during normal walking allows the early detection of postoperative complications such as the tibiofemoral misalignment and soft-tissue imbalance. In addition, the in-vivo data can help to improve the design of TKR in order to reduce polyethylene wear and consequently to increase the lifespan of knee implant. A self-powered custom-designed tibial implant instrumented with four piezoceramics has been developed in order to detect the aforementioned complications by measuring the relative change in pressure center (COP) position for different levels of eccentric compressive loading. Moreover, the energy harvested by the piezoceramics can be used to power a transmission system located at the stem of knee implant to wirelessly transmit the in-vivo data outside the implant for further processing and display.