Healthy 3D knee kinematics during gait: Differences between women and men, and correlation with x-ray alignment

•Knee kinematics in the frontal and transverse planes are different in men and women.•Radiographic hip-knee-angle is weakly correlated with knee abduction-adduction.•Patients should be treated by considering their anatomical and gender differences. Normal 3D knee kinematics during gait is still not well understood, especially regarding differences between women and men. Research question: The objective of the present study was to characterize 3D knee kinematics during gait in healthy women and men with a validated tool. Knee kinematics was analysed with the KneeKG™ system in 90 healthy subjects (49 females and 41 males). 3D knee rotations were compared between women and men, and between right and left knees. Each subject underwent full-length weight-bearing x-rays. Correlations between abduction-adduction angles and lower-limb alignment measures on x-rays were assessed. In the frontal plane, 2.0–5.0° more abduction occurred in women compared to men (0.000 ≤ p ≤ 0.015) throughout the entire gait cycle. In the transverse plane, 2.4–3.7° more external tibial rotation was seen in women than in men (0.002 ≤ p ≤ 0.041) during the initial and mid-swing phases. No difference was found between the right and left knees. Low correlations (−0.52 ≤ r≤−0.41, p