Previous orthopaedic research has indicated a greater prevalence of lower extremity malalignment in obese children during static posture. The purpose of this study is to determine if obese children demonstrate similar dynamic joint malalignment during gait. METHODS: Forty children were classified as obese (age: 10.8±1.4 y; BMI: 24.3±2.7) or non-obese (age: 10.4±1.6 y; BMI: 17.2±1.4). 3-dimensional motion analysis was conducted for five successful trials of barefoot walking at a self-selected pace. Group differences in peak joint displacement and amount of joint motion throughout the gait cycle (calculated as the integrated displacement curve) were analysed using ANOVAs. RESULTS: Non-obese children had greater peak knee (p=0.013) and hip extension (p=0.023) during gait; however, there were no group differences in amount of sagittal plane motion at any joint. Obese children had greater peak hip adduction (p=0.001), and also spent more time in hip adduction (p=0.003) than non-obese children. Obese children had greater peak externally rotated toe progression (p=0.004), and spent more time in this toe-out position (p=0.012). Obese children had greater peak hip internal rotation (p=0.002), and spent more time in hip internal rotation (p=0.004). CONCLUSIONS: Non-obese children showed greater mobility in the sagittal plane, particularly at the hip and knee. Frontal and transverse plane differences suggest that obese children function in a more genu valgum position than non-obese children. Static measures of genu valgum have been previously associated with pediatric obesity; the findings of this study indicate that there are also dynamic implications of such lower extremity malalignment in obese children. Genu valgum presents a greater risk of osteoarthritis for obese children and should be considered when prescribing weight bearing exercise to this cohort.