Fig. 2

Displacement of limb’s mechanical axis in long-leg standing radiographs from pre- to postoperative, subdivided in patients with constitutional varus alignment (negative values of aHKA) a, b and constitutional valgus alignment (positive values of aHKA) (c, d). It can be observed that in presence of constitutional varus alignment a, b the limb’s mechanical axis remains internal to the center of the knee despite the recovery of medial compartment height. Conversely, in presence of constitutional valgus alignment (c, d) the limb’s mechanical axis shifts from internal to external, restoring the valgus alignment that was present prior to the OA onset