Recent advances in remote powering and telemetry permitted the use of sensors inside body. A few studies have been already done on smart knee prostheses, but all focused on monitoring the in-vivo contact forces and moments. A smart design, compatible with mechanical structure of commercially-available knee prostheses, that provides force and accurate kinematics feedback was suggested with all electronics housed in the polyethylene insert (PE). The current work addresses the designed kinematics and force measurement system of that smart implant and its validation in a robotic knee simulator.