Abstract-This paper presents a new and improved orthopaedic surgery simulator. Its capabilities are to analyze, process and display medical images, to reconstruct several three-dimensional models and to integrate them into a virtual environment. The main contribution of this work is to present a new mixed model (surface and volumetric) that allows to simulate bone machining on real time. The application is based on open source software and it also incorporates haptic technology to improve users immersion. The haptic immersion is computed using a 3D-3D collision detector.The system consists of two stages; first, CT's images of a joint are analyzed, and a plan for intraoperative 3D sections is established. At next stage, the user integrates information from the different objects previously generated from the sectioned bones to interact with virtual models and prosthesis. Force rendering is computed using both the surface model and the volumetric model.The developed simulator is particularized on this paper to simulate the cutting of a bone and implementation of a prothesis in a Total Knee Replacement surgery intervention, although other surgical interventions are being modeled currently.