2.5 million knee prostheses are implanted worldwide per year. It is necessary to renew these prostheses from 1 to 15 years after implantation. To date, only x-rays allow us to know the evolution or behavior of the prosthesis (static image in 2d). The BONETAG 4D KNEE project is a collaborative R&D project involving an academic partner: the University of Montpellier through the IES (Institut d’Electronique et des Systèmes), a laboratory specialising in reliable electronic components and systems for observation and measurement, and an industrial partner company BONETAG (PME d’Occitanie — Dpt 66), specialised in the design and development of active implantable medical devices. The purpose of this collaborative project is to develop an on-board system to communicate with knee prostheses using passive RFID technology (without battery), the shape and size of a SIM card that fits into any knee prosthesis brand. This system allows identification, traceability, detection of infection or wear of prostheses. The purpose of this application concerns an additional function: 4-dimensional imaging, i.e. dynamic 3D, during the patient’s walk.