Lower-Limb Kinematic Coordination Strategies During Walking in Individuals with Rett Syndrome

The kinematic gait patterns of individuals with Rett syndrome are often described as highly variable, yet the sources of this variability remain poorly understood. Traditional gait analyses typically summarize movement using discrete kinematic variables, which may obscure underlying patterns of coordination across the lower limbs. The purpose of this study was to apply principal component analysis to multi-joint lower-limb kinematics to identify underlying locomotor coordination strategies in individuals with Rett syndrome. Ten individuals with Rett syndrome walked on a treadmill while three-dimensional lower-limb joint kinematics were collected using a motion analysis system. After processing, the dataset consisted of 600 time-normalized strides (60 strides per participant). Principal component analysis was applied to the stride-by-feature matrix to identify coordinated patterns of joint motion across the lower limbs. Strides with similar principal component score profiles were grouped to define locomotor coordination strategies, and the biomechanical characteristics of each strategy were examined using waveform analysis. The analysis identified nine distinct coordination strategies across the 600 strides. Despite the presence of multiple strategies across the dataset, individual participants primarily relied on a single dominant strategy. Six participants produced the same strategy across all 60 of their analyzed strides, while the remaining participants also displayed strong dominance of one strategy. Further examination of joint excursion magnitude, peak-timing relationships, and inter-joint coordination patterns revealed that the nine strategies could be organized into three higher-level coordination families characterized by (1) constrained lower-limb excursion, (2) moderate excursion with altered timing relationships, and (3) plantarflexion-dominant propulsion patterns. These findings suggest that gait in Rett syndrome is produced through a limited set of biomechanical solutions rather than a single stereotypical gait pattern. Identifying these coordination strategies may provide a framework for understanding gait variability in Rett syndrome, guide individualized therapeutic interventions and potentially serve as a clinical biomarker for evaluating intervention effectiveness.