Dear Eric and Bruce,
Bruce wrote, 'If there were a longitudinal axis to the MTJ, the
PT would not be a good supinator of the LMTJ, because the direction of pull
would be almost parallel to the axis. A muscle can create a moment at all
the joints that it crosses provided it has leverage to do so.
I am convinced such a longitudinal axis exists. This axis is along the sub
talar joint neutral and through the mid cunieform bone, the 'key stone' of
the foot. It is a very necessary long and strong axis. It is the
controller of longitudinal motion from the ankle to the foot. Thus
the 'ankle foot motion' in the sagittal plane can exist to produce a total
universal axis, one of the four we have.
Thus medial to the 'key stone' (2 bones) is the navicular and medial
cunieform bones. These look after supination and abduction,
while lateral to the 'key stone' (2 bones) are the lateral cunieform and
cuboid and these look after pronation and adduction.
This makes the odd number of bones in the foot symmetrical. That is two
move either side while the central bone is neutral. (in the ideal foot).
This only occurs when ALL the foot and ankle joints have normal motion.
I say this because when one is testing these joints individually one can
feel these motions in one direction while being blocked in the opposite.
If the above rules do not apply one has foot motion problems.
Thus in a 'normal foot' the posterior tibial muscle will produce a
hyperflexion and adduction action/force/motion medial to the middle
cunieform and thus produce a pronation (look at the shape of the navicular-
talus joint. It is the only way the joint can procede under a contractory
pressure, ie. from posterior to anterior) and adduction moment.
Exactly what is needed to assist heel off towards toe off with the
standing foot's lock being broken and the running foot commencing to lock
into its position (as the ground surface dictated= moulding) ready for
heel off heading towards toe off.
Its secondary motion is for foot 'elevation'. Dysfunction here is a
totally different kettle of fish.
Bruce,
Could you please explain to me what is meant by:
a) 'uninhibited firing' of the posterior tibial muscle
b)'lateral devication' of the centre of pressure progression
c) 'lateral avoidance'
I have not read or heard of such terms as to exactly what they mean. An
explanation will help me immensely.
Gentlemen, thank you for your time.
Paul Conneely www.musmed.com.au
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