Genu varum patients with medial compartment knee OA showed different gait parameters and intersegmental motion during gait when compared with age- and gender-matched controls. After high tibial osteotomy (HTO), normalized stride length significantly increased with a tendency for increases in gait speed. Before the operation, the midfoot segment compensated in a pronated position in order to acquire a plantigrade foot in a varus alignment of the knee. The effect of HTO was demonstrated by the normalization of midfoot compensation in patients with genu varum.