Differences in gait biomechanics have been observed between obese and healthy weight adults. It is possible that body segment parameters, particularly the thigh, contribute to the differences in knee biomechanics observed during gait between obese and healthy weight adults. The purpose of this study was to determine if increases in thigh circumference and/or mass associated with obesity alter walking biomechanics in healthy weight males and females. Thigh mass and circumference were increased proportional to a 10 unit increase in body mass index. Frontal and sagittal plane knee angles and moments, and temporospatial variables were recorded. For all dependent variables no main effect for gender was observed. Peak knee flexion angle was similar across conditions with no interaction. There was an interaction for peak internal knee extension moment however post hoc comparisons did not reveal differences in condition among males or females. A main effect for condition was observed for peak knee adduction angle, however post hoc comparisons did not reveal differences among conditions. Peak internal knee abduction moment was similar across conditions with no interaction. Stance time and step width increased during the experimental conditions compared to the control. A interaction was observed for stance time. Females had a longer stance time during the circumference only condition compared to the control condition. A greater step width was observed in conditions that increased thigh circumference. Overall, thigh segment parameters altered gait temporospatial variables. Increases in stance time and step width in obese adults compared to healthy weight adults could be a result of their larger thigh segment parameters.