Eric,
In your reply to Bruce, you said:
> How does restriction of motion of the 1st MPJ cause a supination
>moment? I thought you sagittal plane guys were saying that
>limitation of 1st MPJ motion caused pronation of the STJ. (In
>contrast to my belief that STJ pronation causes limitation of the
>1st MPJ). How does FnHL cause both pronation and supination moments?
>
I think you are mixing up two different concepts here. As far as I
understand sagittal theory and FHL, supination in the presence of
dorsal 1st MTPJ restriction is used by some as an *avoidance*
strategy, and therefore is not a forced mechanical consequence of
FHL . Midtarsal pronation, if occurring during late midstance and
propulsion, according to sagittal theory ( and please I do not want
to restart the chicken and egg discussion) , is thought to be a
midfoot deformation (collapse) as a result of dissipation of forward
kinetic energy blocked by restricted hallux dorsiflexion. In this
perspective there is mechanical and causative link between
midtarsal pronation and FHL
Howard and Bruce may fill in here, but according to my clinical
experience, the supinational avoidance occurs in a later stadium of
FHL when the 1st MTPJ starts hurting due to the jamming and the
consequent deterioration of the 1st MTPJ in the many preceding years.
Regards to all,
Bart
--
*******************************************************************
Bart Van Gheluwe
Laboratory of Biomechanics
Vrije Universiteit Brussel -Fac. LK
Vakgroep BIOM
Pleinlaan 2, 1050 Brussel, Belgium
Tel.: 02/629.27.33 (31)
Fax: 02/629.27.36
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