Bruce:

You wrote:

<<Simon and Kevin, I understand your devils advocate position, and I enjoy
the role myself.  I just find it curious that when Inman, and Basmajian
suggest intrinsic muscle activity during the period when the foot needs to
be most rigid for support, therefore supporting Hicks and Boejsen-Moller,
that we would criticize the obvious ( to me anyway) before citing literature
to the contrary!  >>

I don't know what you are talking about here, Bruce.  Please reread my last
post and tell me when I mention anything about muscle function or the other
authors you mention above.  I **have** cited the literature, and have not
criticized Inman, Basmajian, Hicks or Bojson-Moller.

Kevin replied to Jeff:

<<First of all, Jeff, Daryl's paper (Phillips, R.D., Phillips, R.L.:
Quantitative analysis of the locking position of the midtarsal joint.  JAPA,
73:518-522, 1983) did not measure the range of motion of the midtarsal joint
(MTJ).  He measured the forefoot to rearfoot relationship at three different
subtalar joint (STJ) positions.  Therefore, not only was the range of motion
of the MTJ not measured in Daryl's study, but there is also no way that the
assumption could be made that an exponential relationship exists from the
three data points on a curve that was illustrated in his study.  More than
three data points are needed to suggest that an exponential relationship
exists.

..........

Do we know this?  Also, since the MTJ doesn't have a "neutral position" then
one could also say that the supination range of motion available at the MTJ
increases as the STJ pronates?  I personally am not convinced that we can
say with good confidence that the "pronation" range of motion increases in
the MTJ as the STJ pronates.  However, I can say that the available range of
motion of the MTJ seems to increase in most feet as the STJ pronates.

...........

Again, are we actually increasing "MTJ pronation" as the STJ pronates.  What
study has ever shown this to be the case?  I don't know of any.

Just because the forefoot to rearfoot relationship changes to a more
"everted" position with pronation of the STJ simply means that the medial
and lateral columns of the foot are in different spatial relationship to
each other at each point within the STJ range of motion.  It doesn't
necessarily mean that the MTJ is "more pronated".

This gets to the point that Simon and I are trying to make here.  If we
don't acknowledge that the MTJ is not the only joint that allows the plane
of the metatarsal heads to change relative to the rearfoot, then we are
doomed to repeat the theoretical mistakes of the past.  I want to head
forward, not stagnate in the past.

...........

You mention that the 1st ray and 5th ray are primary joints of the foot, but
which joints do they consist of?  Don't they include the navicular-cuneiform
joint, cuneiform-metatarsal joint and the cuboid-metatarsal joint?  Why not
just consider all the individual metatarsal rays to have some motion in them
since this is clinically apparent and shown in the research by Ouzounian and
Sherreff that Simon mentioned.  Then, once you have accepted the fact that
not only are the 1st and 5th rays primary joints of the foot, but also the
2nd, 3rd and 4th metatarsal rays are primary joints of the foot, then we can
just **throw out** the concept of the longitudinal axis of the midtarsal
joint since the clinical observations which use the longitudinal MTJ are
much more adequately and accurately described using the concept of
differential dorsiflexion-plantarflexion of the individual metatarsal rays
which occur in all weight-bearing activities, including Daryl's study.>>


Sincerely,

Kevin

*****************************************************
Kevin A. Kirby, DPM
Assistant Clinical Professor of Biomechanics
California College of Podiatric Medicine

Private practice:
107 Scripps Drive, Suite #200
Sacramento, CA  95825

Voice: (916) 925-8111   Fax: (916) 925-8136
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