Knee functional calibration strengthens the relationship between lower limb bone morphology and hip rotation during gait.

The position of the femur's greater trochanter is crucial to produce the required hip abduction moment during gait. Clinical parameters describing the shape of the femur, such as femoral neck anteversion and neck shaft angles, influence the lever-arm of abductor muscles. In children with cerebral palsy, abnormal lower limb bone shapes may impair function, highlighting the importance of clinical gait analysis for surgical decision. Here, we re-examined a dataset on the correlation between 3D lower limb bony morphology and hip rotation kinematics during gait. This study was a secondary analysis of a dataset from 121 children with cerebral palsy. 3D bony morphology was determined by a bi-planar, low dose, digital x-ray system and gait analysis utilised the conventional gait model with or without two functional knee calibration algorithms. The results indicated that functional calibration improved the variance explained by linear regression models between 3D bony morphology and the mean hip rotation during gait. Furthermore, femoral neck anteversion and neck shaft angles were now identified as significant predictors in the models. Despite differences between the functional algorithms, results of the associated regression models were similar. However, bony morphology alone did not fully explain hip rotation, suggesting other factors are involved. We noted limitations in functional calibration due to soft tissue artifacts and insufficient knee range of movement. Previous results on the relationship between bony morphology and gait may be revisited considering the findings of this study.