Chalmers BP, Kolin DA, Mayman DJ, et al. - The present study was performed to define anatomic femoral rotational axes in patients undergoing primary total knee arthroplasty (TKA). Researchers distinguished 100 individuals that had undergone a primary TKA with a preoperative CT scan. They assessed angles between the surgical epicondylar axis (SEA) and the AP axis to the posterior condylar axis (PCA) independently by a musculoskeletal fellowship-trained radiologist and a fellowship-trained arthroplasty surgeon. The results of this study exhibited that the normal anatomic rotational axes of arthritic knees are highly variable, with a 10° range in the SEA and a 16° range in the AP axis. It was shown that routinely setting femoral rotation 3° external to the PCA will yield a significant error in aligning the femoral component with either the SEA or AP axis.