Influence of Axial Rotation Between the Femoral Neck and Ankle Joint on Kinematics in Normal Knees: A Cross-Sectional Study.

Abstract

The effect of axial rotation between the femoral neck and ankle joint (total rotation [TR]) on normal knees is unknown. Therefore, this study aimed to investigate the TR effect on normal knee kinematics. Volunteers were divided into groups large (L), intermediate (I), and small (S), using hierarchical cluster analysis based on TR in the standing position. TR was measured using three-dimensional (3D) bone models generated from CT. A two-dimensional to 3-dimensional registration technique was used to assess the spatial position and femur and tibia orientation during squat. The axial rotation, varus-valgus alignment, and anterior-posterior translation of the femur relative to the tibia were evaluated. Group L had the highest TR, whereas group S had the lowest TR (L: 36.6° ± 6.0°, I: 23.2° ± 3.0°, and S: 13.8° ± 5.1°). Above 50° of flexion, femoral external rotation was greater in group S than in groups L and I. From 40° to 110°, the medial side was more anterior in group L than in groups I and S, whereas the lateral side was more posterior in group S than in groups L and I. Individuals with larger TR had more femur anterior-medial translation relative to the tibia.