In this paper a methodology for knee bones models 3D printing from DICOM series of images is presented. It would be very useful for doctors to see real models of knee bones and ligament attachment sites onto both bones before the ACL reconstruction. With physical bone model, orientation and position of operative equipment (tibial and femoral guides) could be planned before the operation. This could lead to more precise ACL reconstruction. In the introductory part of this paper ACL reconstruction method and some problems that may occur are presented. After that, model of procedure for knee bones 3D printing is shown. First, a procedure for 3D knee bone models generation is shown. For this purpose a program system is developed based on the VTK library. Generation of femoral transverse axis which enables tibial bone to rotate about femoral bone is very important. This axis enables knee flexion and extension and in ACL reconstruction, doctors rotate tibial bone about femoral bone which is fixed. Point clouds of femoral bone condyles are used for calculation of centres of best fit spheres of both condyles by least squares method. After that bone models are prepared for 3D printing. Because of the MakerBot Replicator 2X printer limitations, model of the knee is printed in two parts which are then glued together.