Just got back from teaching in South Africa. One of the topics I taught on was the influence of foot orthoses at the midtarsal joints (MTJ): calcaneo-cuboid joint(CCJ) + talonavicular joint (TNJ)= CCJ + TNJ= MTJ. As we know, joints don’t “lock”, therefore it seems reasonable to assume that some of the influence in MTJ stiffness change observed with variable positioning of the subtalar joint should be due to changes in the 2nd moment of area (it’s stiffer because it’s thicker) due to the orientation in the articular surfaces of the CCJ and TNJ with varying subtalar joint (STJ) positions and the MTJ “stacking” as a result of this- see diagram attached.
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Foot orthoses and the MTJ