To explore a method for measuring the bowing angle of the femur in patients with knee varus.

The patients with knee varus knee osteoarthritis treated in the department of orthopedics, Shuguang Hospital affiliated to Shanghai university of traditional Chinese medicine from January 2014 to June 2018 were selected. The previous full-length X-ray films of the lower extremities were compared with the femoral X-ray of the varus knee. Two of the most similar femur X-ray films were determined, and the corresponding rotation angle of the projection was recorded.

The suitable rotation angle of the femoral X-ray in knee osteoarthritis patients with knee varus were as follows: the group of 10°≤varus angle<20°∶ 10°(9°, 12°); the group of 20°≤inversion angle<30° ∶ 16°(14°, 20°); inversion angle≥30°group 24°(21°, 25°).

For the osteoarthritis patients with genu varus, the lateral arch angle of the femur can be more accurately measured by appropriate external rotation when taking the femoral X-ray film.