If the foot is abnormally pronating and causing problems, there is only one way it can be stopped. It has to be stopped by the use of a force on the medial side of the assumed subtalar joint axis. While this makes intuitive sense, the problem arises as the position of the axis varies substantially. There are clinical tests that can tell us where the axis is, so we can work out where the force from a foot orthoses has to be applied.
When the axis is located more medially located, the problem comes that there is very little room on the plantar surface medial to the joint axis for that force to be applied. To apply the force various orthotic design parameters have been developed. There is the DC Wedge, Kirby medial skive, the the Blake Inverted foot orthotic.
Recently a unique design, the MOSI foot orthotic has been proposed by Paul Harradine, and Simon Collins., Chris Webb , Lawrence Bevan. The MOSI orthotic stands for medial oblique shell inclination. The aim of this design is to incline upwards the shell of the orthotic on the medial side of the subtalar joint axis. It is an interesting innovative design that makes good theoretical sense.
