Navicular drop and first metatarsophalangeal joint motion

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An investigation of the dynamic relationship between navicular drop and first metatarsophalangeal joint dorsal excursion
Nicole L. Griffin, Charlotte Miller, Daniel Schmitt, Kristiaan D'Août
Journal of Anatomy; Early View

 

When it becomes available, I'd love a copy if anyone can get it.

Howard Dannenberg and I have long been going back and forth on whether the limitis causes the foot drop or the foot drop causes the limitus.

A couple of possible explanations of why navicular drop does not explain hallux dorsiflexion in gait. Hopefully they looked to see if range of motion was available in the first place. A functional limitus may behave differently than a structural limitus. There are different types of pronators. There are muscular pronators and there are ground reactive force pronators. The muscular pronation usually occurs around heel lift and this could be the navicular drop that they see. The ground caused pronators will tend to pronate to their end of range of motion during the contact phase. If navicular drop was measured after this time then there would be some people who would be fully pronated with high medial forefoot loads without navicular drop. Whereas the late midstance pronators would have navicular drop and then may achieve high loads sub first ray (met and toe). (High loads sub 1st ray and prnonation is what you need for the plantar fascia to become tight and limit first toe dorsiflexion.

Of course, another factor is STJ axis position. If you have two people with equal navicular drop and one has less hallux dorsiflexion then you'd expect the one with the more medially positioned STJ axis to have less dorsiflexion if the muscle activation was the same.

Eric.

 

See also:
http://www.japmaonline.org/content/96/4/313.short