Objective：This study aims to provide references on the rotation of the femoral component during total knee arthroplasty (TKA)by measuring the rotation degree of the surgical transepicondylar axis and the posterior condylar axis of the femoral condyles on CT images. Methods：The X - ray and lower extremity CT imaging data of 283 patients who underwent TKA in the Department of Bone and Joint Surgery，the First Affiliated Hospital of Nanjing Medical University from October 2018 to March 2022 were retrospected in our study. One resident and one senior chief physician of joint surgery measured the angle between the surgical transepicondylar axis (sTEA)and the posterior condylar axis(PCA)by the imaging system，respectively. The angle between sTEA and PCA and the angle between femoral component and sTEA after routine placement of the femoral component with reference to 3° external to the PCA was calculated. Results：The sTEA was on average 1.63° externally rotated to the PCA(range 3.79° internal to 7.87° external). When the femoral component was routinely placed at 3°external to PCA，only 163(57.6%)patients had femoral component rotation within ± 2 ° of sTEA after TKA，of which 68(24.0%)patients had femoral component internal rotation to sTEA. Conclusion：There were extensive differences in the rotation of the distal femur in patients with osteoarthritis. Routinely setting femoral rotation 3° external to the PCA would cause significant position errors in femoral component，affecting the prognosis of TKA. Joint surgeons should individualize the rotational alignment of the femoral component during TKA based on preoperative imaging data.