Ontogenetic changes in femoral morphology and joint loads in children.

Aims: This study aimed to quantify ontogenetic changes in femoral morphology - specifically femoral head and condyle sizes - and joint loads in children. Methods: MRI and 3D movement data were recorded from nine children without any known pathologies at two timepoints, two years apart. Femoral geometry was segmented from the MRI to quantify femoral head and medial and lateral condyle volumes. Personalized MRI-informed musculoskeletal models were created and used to estimate hip and knee joint contact forces (JCFs) based on the 3D movement data. Multiple linear regression models were used to assess whether changes in JCF and femoral morphology can be predicted from simple measures such as age, body weight, and height. Results: Both femoral joint contact geometry and absolute JCF significantly increase with age. However, when normalized to body weight, JCF remained stable - or even decreased in the case of medial condyle JCF - over time. Predicting changes in JCF based on the simple measures of age, weight, and height worked reasonably well for hip JCF (R Conclusion: Our findings demonstrate ontogenetic increases in both absolute JCF and joint contact surface areas, which may help maintain relatively stable cartilage pressures during growth. These data provide valuable reference values for differentiating normal developmental patterns from pathological alterations in femoral morphology and joint loading. While simple regression models effectively captured population-level trends, they were not suitable for subject-specific predictions, underscoring the need for more advanced and individualized modelling approaches in paediatric biomechanics.