Dependency of coronal lower limb alignment on lower limb configuration: A sex-specific analysis

Accurate assessment of coronal knee alignment is important for the management of knee joint injuries and diseases. The lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) measured on anteroposterior radiographs are key indicators. Geometrically, the configuration of a hexagon formed by the centers of the hips, knees, and ankles is hypothesized to influence LDFA and MPTA. Considering the sexual dimorphism in skeletal configuration, this study aimed to investigate the relationship between lower limb hexagonal configuration and knee alignment in each sex. A total of 210 standing long-leg radiographs were obtained from patients (mean age 62.8 years) visiting a single hospital for knee-related concerns. Knees with minimal osteoarthritic changes were selected. Inter-capital distance (ICD), defined as the distance between the centers of the femoral heads, femur length (FL), tibia length (TL), and total leg length (TLL) were measured. The parameters were compared between the sexes. Relationships between parameters, their ratios [adjusted for height (Ht) or TLL], and knee alignment were analyzed. The influence of demographic factors was also assessed. TLL, FL, and TLL/Ht ratio showed significant correlations with LDFA both in males and females. TL and ICD correlated with LDFA only in males. TL correlated with MPTA in both sexes, whereas Ht was associated with MPTA only in males. In females, TLL, FL, ICD/TLL, and TLL/Ht showed correlations with MPTA. Coronal knee alignment was dependent on lower limb configuration. • Coronal lower limb alignment can be compared to the side lines of a symmetrical hexagon. • Dependency of inclination of side lines on configuration of hexagon would be understandable. • Coronal alignment was hypothesized to depend on whether the hexagon was flat or narrow. • Side lengths of the hexagon were measured on standing long-leg radiographs. • Dependency of coronal alignment on lengths and length ratios in sex-dependent manner.