['The posterior femoral offset may significantly impact the final flexion range after total knee arthroplasty (TKA). The purpose of the present study was to compare a conventional, radiologic-based technique with an intra-operative, surgical navigation-based technique for the measurement of posterior femoral offset. The tested hypothesis was that the two measurement techniques produce different results both before and after TKA.', 'One-hundred consecutive cases referred for end-stage knee osteoarthritis have been studied. Posterior femoral offsets, measured pre- and post-TKA from radiographs, as well as those measured from a navigation system intra-operatively, were analysed. The pre-TKA measured offsets, post-TKA measured offsets and the changes (pre- vs. post-TKA) in the offsets were statistically compared between the radiologic and the navigated measurement techniques at a 0.05 level of significance.', 'The mean paired difference between pre-TKA radiologic and navigated measurement was 4\xa0±\xa04\xa0mm (p\xa0<\xa00.001). There was a significant and moderate positive correlation with a good coherence between the two measurements. The mean paired difference between post-TKA radiologic and navigated measurement was 6\xa0±\xa05\xa0mm (p\xa0<\xa00.001). There was a significant and moderate positive correlation but a poor coherence between the two measurements.'] Is radiographic measurement of the posterior femoral offset precise?