A hardware-assisted intensity-based registration method developed for assessing patellar tracking was discussed. It was also proposed to generate digitally reconstructed radiographs (DRR) in real time without any precomputation for 2D/3D registration. The CT slices were first transferred to the texture memory of the video card and a particular pose was rendered by setting the camera geometry according to the information from fluoroscope calibation, to generate a DRR. The results shows that hardware generation of DRRs did not need precomputation and was 25 times faster than software computation. The main advantage of the method was that it allowed the assessment of patellar tracking to be done using commonly available graphics hardware.