Abstract: The invention relates to a set of motion sensing devices HS mounted above and below the injured joint, a mobile application MobApp that receives sensor data, and a web server WS. The mobile application comprises a physiotherapists interface MPTI and a patient interface MPI, an Exercise definition module EDM, an assessment module ASMD and the movement analysis module MAM. The physiotherapist interface MPTI shows the patients their progress, the list of scheduled exercises, receives feedback and delivers assessments. The web server WS hosts a cloud-based database DB which keeps the relevant data, a Machine learning unit MLU and a physiotherapist interface WPTI. The claimed method, ensures an optimized monitoring of the physiotherapy of joints, by neutralizing within the Calibration and compensation unit CCU the influence of the position and drift of the motion sensors and also by implementing the Machine learning unit MLU and relevant algorithm.