This preliminary study presents a new predictive assessment of the post-operative knee laxity, represented as 3D bone isosurface maps. For a given laxity test, the virtual graft-Elongation Map (EM) shows the corresponding laxity values for each possible femoral insertion tunnel. A biomechanical model is used to estimate these values After Reconstruction (AR) from Before Reconstruction (BR) navigated data. Combined EM (CEM) is then computed to synthesize all the EM information in order to assist the surgeon in choosing the best ACL femoral insertion candidate.