Kevin wrote,

>>the STJ axis will be less medially deviated, and then gastroc-soleus contraction will produce a greater STJ supination moment than what it would have otherwise.  In
addition, the deep flexors and peroneals, which are also active in late midstance, will either have increased magnitudes of STJ supination moment and/or decreased magnitudes of STJ pronation moment to further increase the net STJ supination moment (or decrease the net STJ pronation moment) during late midstance.  Focusing just on the windlass effect as the cause of
resupination is certainly not telling the whole story of why resupination occurs in late midstance and propulsion in many feet.>>

Kevin,

Well said and quite correct.  My only addition is that without TIMELY 1st MTP joint dorsiflexion, the entire system falls apart. The moment arms would increase so significantly that the contraction efforts of the supporting musculature would be incapable of creating the effects you describe.  This is why I have taken the position I have.  The foot is specifically designed with the sagittal break at the MTP joints.  This permits peroneal stabilization of the 1st ray while heel unweighting and eventual lift off occur.  If MTP joint motion fails to occur on time, then the same force which would lift the heel and create propulsion and stability, instead creates pronation.  Viewing this process with in-shoe pressure measurement makes this obvious.  Visual observation is insufficient to discern the subtle nature of the changes which occur, particular in the early stages of single support phase.

From my observations, posting the RF caused the CoP to move laterally, unweighting the 1st ray and permitting an avenue for plantarflexion.  It is certainly one way to manage the pathomechanical process.  An other approach is to avoid RF posting if the CoP flow is already lateral, and manage 1st MTP dorsiflexion with cutouts, kinetic wedge extensions, digital posts, etc.  Each method has a definite place in treatment process, however, there is a downside to RF posting when weight flow is already lateral, as in the flexible FF valgus foot type.  This is particulary true in management of plantar fasciitis in this foot type, and RF posting can and does exacerbate this condition.  Podiatric biomechanics is a very individual business, and precise visualization techniques of what happens WHILE WEARING SHOE GEAR AND WALKING is essential for positive outcomes.

Regards,
Howard Dananberg

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