Forefoot Varus
Forefoot varus is an uncommon biomechanical dysfunction of the foot that causes the foot to pronate. It is due to a bony deviation that causes the foot to pronate or flatted to get to the ground. The only way to manage this type of flat foot is with foot orthotics. No amount of exercises or muscles strengthening will change anything, as the foot as to flatten to get to the floor.
Determining if forefoot varus is actually present or not is crucial, as there are potential problems if it is diagnosed as being present when its not (see this). The idea being is that if you use a forefoot varus post when there is no forefoot varus, then this will jam up the first pay to end range of motion and potentially be painful (more on this). Most cases of forefoot varus get confused with the soft tissue version of forefoot supinatis (link). There is a good collection resources here on this issue and its importance.