The mechanism of the static effects of the wedged insole for the medial osteoarthritic knee was studied in ten women. They stood with one leg on the wedged sole board, and the change of the position of the line through the center of gravity, the femorotibial angle, the tibiocalcaneal angle, and the spatial position of the whole lower limb were investigated using load transducers and roentgenograms. When the subjects stood on the wedged sole board, the line through the center of gravity and femorotibial angle did not change. The change in the spatial positions of the lower limb (p less than 0.02), i.e., the mechanical axis of the lower limb near an upright position, and the change of the calcaneus to valgus direction in the subtalar joint (p less than 0.01) were observed. These changes were considered from two-dimensional analysis to reduce the excessive loading on the medial joint surface and the excessive tensile force of the lateral side. The wedged insole thus proved effective for the conservative treatment of the medial compartment osteoarthritic knee.