Changes in 3D joint dynamics during the first 5 months after the onset of independent walking: a longitudinal follow-up study.

A longitudinal follow-up study of 10 normally developing children was performed in order to identify changes in mechanical control of gait during the first months after initiation of independent walking. Changes in spatio-temporal parameters and kinematics were recorded (336 trials spread over 83 recording sessions) and linked to kinetic features of gait. At the onset of independent walking, all children in our study group showed the same walking strategy: a dominance of the extending moments around the lower extremity joints was observed and could be linked to the flexed position of the hip and knee during stance. In a subset of our study population, the dominance of the extending moments disappeared with increasing walking experience, though reversal to immature patterns was frequently observed. A linear mixed model showed that with increasing walking experience, there was an increase in dimensionless walking speed, dimensionless cadence and dimensionless stride length (without correction for the increase in speed). Maximal hip extension in stance, knee flexion and ankle plantar flexion at foot contact also increased (even when the increase in speed is taken into account). Dimensionless step width, duty factor, double support time, maximal hip flexion in swing and hip abduction significantly decreased (with correction for speed). Important changes were also observed in ground reaction force patterns, evolving towards a double "hump". No significant changes could be observed in other kinetic parameters, probably due to the high degree of variability.