Radiographic brightness was measured in the proximal tibia and patella of 57 knees before and after high tibial osteotomy (HTO) for osteoarthritis. The brightness was converted to the thickness of a reference Aluminum phantom
using NIH Image software. The knees were classified into 4 groups according to the position of the point at which the mechanical axis of the leg intersects the tibial articular surface after HTO, namely "overcorrected" (the position; lateral 0～25%), "adequately corrected" (mid lateral 25～50%), "undercorrected" (mid medial 50～75%), and "correction failure" (medial 75%～). Brightness was high in the lateral and central regions of the proximal tibia in the adequately corrected group, while that of the lateral loading region was high in the overcorrected group. The brightness was broadly high in the undercorrected group, and was not distinct in the correction failure group. In the patella, the brightness of the lateral region was higher than that of the medial region before HTO, and the difference between the two regions was considerably reduced in the adequately corrected group. These findings indicate that adequate correction of leg alignment causes favorable changes in the patellofemoral joint as well as in the femorotibial joint.