When the wedge is in place, the foot does not need to collapse so as to come in contact with the ground. This collapsing motion of the foot is referred to as pronation. Because the leg is connected to the foot at the ankle, for every 1 degree of wedge in the orthotic, 1 degree of internal rotation of the foot is stopped.
The collapse of the foot (pronation) is the abnormal motion that occurs when we walk and stand that causes stress on all of the joints, tendons, and nerves that make up the foot. The internal rotation of the leg that is directly related to the collapse of the foot is the motion that places stress on the structures of the leg and knee.
The amount of wedging in the orthotic design ultimately determines how much of the unwanted motion in the foot and leg is stopped. This is directly related to the stress on all of the anatomical structures, and the pain, symptoms, and deformity that result.
When the wedge or orthotic device is in place, breakdown of the foot is limited and stress on the structures is diminished. When stress on the structures is diminished, pain and deformity are reduced.