Body Mass Index is Related to Femoral Anteversion, Hip Rotation During Gait, and Passive Hip Range of Motion in Children and Adolescents.

Background: Overweight and obesity are major global health issues, often linked to orthopaedic problems, skeletal malalignments, and altered gait biomechanics. However, skeletal and biomechanical adaptions in the transverse plane remain underexplored. Therefore, this study aimed to investigate the relationship between body mass index (BMI) and variables describing lower extremity torsional profiles, hip rotation mobility, and transverse plane gait characteristics in children and adolescents.

Methods: Acetabular and femoral anteversion, tibial torsion (measured through computed tomography), hip and knee rotation, and foot progression angles during the stance phase of gait (measured by 3D gait analysis), as well as passive hip rotation range of motion (evaluated as the midpoint of hip rotation in clinical examination), were retrospectively analyzed in 122 children and adolescents. Correlations between all variables and logit-transformed BMI percentiles were calculated.

Results: Moderate correlations were found between BMI percentile and hip rotation during the stance phase (r=-0.68, P<0.001), the passive midpoint of hip rotation (r=-0.51, P<0.001), and femoral anteversion (r=-0.50, P<0.001). Small correlations were observed for acetabular anteversion (r=-0.36, P<0.001), knee rotation during stance phase (r=0.34, P<0.001), and foot progression angle during stance phase (r=-0.31, P<0.001). Tibial torsion showed a nonsignificant negligible relationship with BMI percentile (r=-0.26, P=0.004).

Conclusion: BMI percentile was positively correlated with external hip rotation during the stance phase of gait and passive external hip rotation, and negatively correlated with femoral anteversion. These findings suggest abnormal body weight is associated with static and dynamic biomechanical alterations. Therefore, weight management should be considered in orthopaedic assessments and treatment planning for children and adolescents.