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"Biomechanics Corner": Overpronation

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  #1  
Old 26th October 2009, 07:02 AM
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Default "Biomechanics Corner": Overpronation

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I am Grateful to the SCP and the "Podiatry Now" team for permission to reproduce this months "Biomechanics Corner" Column on Podiatry Arena.

I'd hoped this months column would provoke a debate. I've had three emails regarding it already and I've not even had my copy yet (damn postal strike)

This is the column as I submitted it.

Quote:
Overpronation On Trial

Last time we looked, in brief, at one concept of modern biomechanics. This month I'd like to flit back a few years and look at one of the fundamental pillars of more traditional biomechanics. In particular I'd like to examine a word and concept which always makes me froth at the mouth and go purple (think the Incredible Hulk but less green). Overpronation.

For the sake of brevity I'll talk overpronation, but one could insert any of its more pretentious but basically synonymous cousins, hyperpronation, pathological pronation and excessive pronation (and any others you can think of).

As a Biomechanics Lead I have mentored many graduates and undergraduates in the "dark arts" of biomechanics. Part of this process involves looking at assessment files. One of these generalisations seems to come up in almost every file I see! I see it also in referrals and frequently hear it from patients, especially those with access to Google. But does it belong in the "diagnosis" box where I generally find it? What, when you get down to it, does overpronation MEAN?

To examine overpronation we must first consider what constitutes pronation. Any fresh shiny graduate can tell you that pronation is a movement at the sub talar joint comprising Eversion, Abduction and Dorsiflexion. A more interesting question is why, if it causes so many problems, does pronation occur?

Two functions are generally offered for pronation; shock absorption and adaption to uneven ground surfaces. Both vital things to protect joints further up in the chain. It is easy to forget in our righteous passion for supinating the foot, that pronation is a natural and necessary movement which is an integral part of a healthy gait and function. I'll repeat that. Pronation is both normal and beneficial to the patient and its ABSENCE can increase the risk of pathology.

Some would have us believe that the proximal structures, knees, hips, pelvis etc are only “aligned” when the feet are in Sub Talar neutral, that they are “designed” to work in that position and that if the foot pronates at all that they are “out of alignment”. Dear reader, this is not the case and the seminal work by Root et al never suggested it was!1 THAT belief has been born since. It is, perhaps, impolitic to speculate on who would stand to gain, financially, from propagating the belief among podiatrists and other health professionals that a situation seen in the vast majority of normal, healthy feet is pathological and in need of “correction”. And there I will stop with that line of speculation, as the smell of boiling tar is thick in the air and I see a few feathers waft past in the breeze. The truth, as agent Mulder astutely observes, is out there for those who seek it.

The "measure" I see most often used is static weight bearing. The patient stands and the clinician looks owlishly at the ankle (or if they are really keen a bisection of the calc). "Aha", they say "you're feet are pronated / overpronated / roll in. There's your problem right there".

Let us consider for a second how a normal healthy foot with a nice healthy function will appear in relaxed stance. The orientation of the Sub Talar Axis means the centre of mass will tend to come down on the pronation side of the line, so the foot will pronate until something stops it. What structures limit pronation? The Tibial muscles group certainly, but it would not be efficient for them to hold the patient in supination when in relaxed stance. The planter fascia / windlass? Sure but there is not a lot of tension there before heel raise (in most patients). Bony osseous limitation? Hope not, unless you are really arthritic! I contend that in most cases the limiting structure is the Deltoid ligament complex which limits the range generally. And what position will that keep the STJ in? Pretty near the maximally pronated position. It represents a position the foot CAN achieve and little more than that. It does not indicate the degree to which the calc everts during gait 2, 3 . The position of a “normal” healthy, effectively functioning foot during static weight bearing may be closer to maximally pronated than neutral, its is certainly not neutral!4

Keep in mind also that correlation is not the same as causation. Just because a foot which hurts also pronates does not infer that it hurts BECAUSE it pronates.

“Overpronation” is at best a vague observation with little diagnostic value and different meanings to different people. It covers so much variation of pathological function that it actually informs the reader of little of value. All it tells me when I see it in a file is that A: the foot pronates (which it should) and B: the patient has a pathology of some description. One can be pretty sure that the foot pronates; after all it would be pathological if it didn’t. So by inference all diagnosis of “overpronation” means that the assessor has blamed the pathology on a generally benign movement. It does not tell me why that benign movement has become pathological.

If we wish to make meaningful observations I believe we must rise above the “pronation causes all ills” school of thought to which so many other AHPs subscribe when they “dabble” in biomechanics. Pronation is a complex, benign system which can malfunction in a variety of ways which can cause a variety of pathologies. How exactly it malfunctions may inform what problems it causes and what type / prescription of insole will work most effectively at treating it and that is where we, as the professionals with the most knowledge of feet should excel. Simply ascribing all pathology to “pathological pronation” and treating with “anti pronation devices” or even (heaven forbid) “arch supports” may have a success rate, but it does not elevate us far above the man I saw at a boot fair selling “orthopaedic arch supports” from the boot of his car at £15 per pair (2 for £20) last weekend for the treatment of every musculoskeletal pathology a suffering body can be plagued by.


1. ROOT ML, ORIEN WP, WEED JH: Normal and Abnormal Function of the Foot, Vol 2, Clinical Biomechanics Corporation, Los Angeles, 1977

2. HAMILL J, BATES BT, KNUTZEN KM, ET AL: Relationship between selected static and dynamic lower extremity measures. Clin Biomech 4: 217, 1989

3. MCPOIL TG, CORNWALL MW: The relationship between static lower extremity measurements and rearfoot motion during walking. J Orthop Sports Phys Ther 24: 309, 1996.[

4. KIRBY KA: Biomechanics of the normal and abnormal foot. JAPMA 90: 30, 2000
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Old 28th October 2009, 04:09 PM
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Default Re: Biomechanics Corner - Overpronation

Robert

Just wanted to say thank you for putting so eloquently what I have been banging on about for ages and can't get half my colleague to understand and move away from! I intend to ensure that as many pods, physios etc etc as I can find read, digest and NEVER again send me a referral with "overpronation" written as a diagnosis - a thing most likely to see me turn an interesting shade of purple and start shouting at the piece of paper!

Thank you - and I hope you haven't been bombarded with emails from those that haven't yet seen the light!
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Old 29th October 2009, 02:45 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
I intend to ensure that as many pods, physios etc etc as I can find read, digest and NEVER again send me a referral with "overpronation" written as a diagnosis
Good luck with that! If you find a way PLEASE let me know how you did it!

Quote:
Thank you - and I hope you haven't been bombarded with emails from those that haven't yet seen the light!
Its been very gratifying, 7 so far! Some in support, some thoughtful and some very anti!

I consider all of them to be positive, because whether or not you happen to agree with my individual opinion (which is all it is) it means that 7 people have thought about their practice in sufficient depth to put pen to paper (or fingers to keyboard.

Some of them make some excellent points. When I get time I'll post a few and answer them here. And if you are one of the stalwart reflective clinicians who wrote to me, bless your heart. I will get back to you if I've not already done so!

Thanks
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Old 29th October 2009, 02:50 AM
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Default Re: Biomechanics Corner - Overpronation

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Originally Posted by Robertisaacs View Post
I consider all of them to be positive, because whether or not you happen to agree with my individual opinion (which is all it is) it means that 7 people have thought about their practice in sufficient depth to put pen to paper (or fingers to keyboard.

Some of them make some excellent points. When I get time I'll post a few and answer them here. And if you are one of the stalwart reflective clinicians who wrote to me, bless your heart. I will get back to you if I've not already done so!

Thanks
Will these be published in the journal?
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Old 29th October 2009, 02:59 AM
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Default Re: Biomechanics Corner - Overpronation

Many years ago I was slightly offended when at a function I spoke at ,an orthopod asked if all Podiatrists belonged to the "save the pronated foot brigade'. Over -pronation against what given norm in relation to each individual. Do we keep looking for what we want to see (ie position over function) as it is easier to sell the concept to the patient or harder for some practitioners to understand the complexities that produce the forces that the foot/leg sustain during use and activity.
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Old 29th October 2009, 03:02 AM
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Default Re: Biomechanics Corner - Overpronation

Rich,

What did said Orthopod quote as the 'given norm for each individual'?

Ian
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Old 29th October 2009, 03:10 AM
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Default Re: Biomechanics Corner - Overpronation

the year was 1988 I was younger and details apart from what then was a perceived slur are foggy. His general gist was what is normal and why was pronation the root of all evils for lower limb pathology. Valid line actually and got me interested in other modalaties of treatment options
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Old 29th October 2009, 03:55 AM
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Default Re: Biomechanics Corner - Overpronation

a quite day feel like playing devils lawyer

Quote:
In particular I'd like to examine a word and concept which always makes me froth at the mouth and go purple (think the Incredible Hulk but less green). Overpronation
I´m not sure why this makes you froth etc While I get your point that Over is not the best word But if we take excessive or even too much which to me mean about the same thing. These can all be considered a bad thing especially when considering SALRE. Yes I agree that Pronation is normal and very important and that there is no such thing as the normal amount of pronation.

But I think we tend to forget that the movement of Pronation will mean that the STJ axis medially deviates. Ie at the Talus adducts and plantarflexes during CKC this change in talus position will cause the STJ to medially deviate. ( A STJ internal pronation moment )

Here a quote from Kevins paper.

Subtalar Joint Axis Location and Rotational Equilibrium Theory of Foot Function
Kevin A. Kirby, DPM, MS* J Am Podiatr Med Assoc 91(9): 465-487, 2001

Quote:
It has been determined that closed kinetic chain
subtalar joint pronation causes plantarflexion and internal
rotation of the talus and closed kinetic chain
subtalar joint supination cause dorsiflexion and external
rotation of the talus in relation to the plantar
calcaneus and the ground.1, 3 Previous anatomical investigations
also have noted that the subtalar joint
axis consistently pierces the talus anteriorly at the
superior aspect of the talar neck.2, 5, 6, 8, 12 Therefore,
as the talar head and neck rotate and translate within
space in relation to the plantar foot and ground during
closed kinetic chain rotational motions of the
subtalar joint, so does the subtalar joint axis rotate
and translate in relation to the plantar foot and
ground during these same motions
Right so as the STJ pronates there will be medial deviation of the axis. Which will mean that the external factors ligaments medial to the stj axis , muscles medial to the stj axis , GRFmedial to the stj axis , bone medial to the stj axis etc will all undergo increased force. The soft tissue will then require increase force to resupinate the foot.

Both the medial deviation and the attempt to resupinate ( lateral deviate the axis ) can lead to pathological complaints.

Too much STJ pronation increased medial deiviation of STF axis more force applied during STJ pronation more force required during STJ resupination more pathological complains.

Right I think I´m about to become a punching bag but here my statement Overpronation is a diagnosis as long at the person writing the statment understands what the cause to STJ pronation will be on the STJ axis location.
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Old 29th October 2009, 04:20 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
Will these be published in the journal?
Only if people write to the journal, which I would encourage anyone to do!

Quote:
a quite day feel like playing devils lawyer
Bless yew kind sir!. I'd hoped somebody would!

I'm between patients (damn them) so i'll kick off with a quick one.

Quote:
But if we take excessive or even too much

What is the defining characteristic of "too much"? Is a matter of degrees or whether the foot has a pathology.

Quote:
Overpronation is a diagnosis as long at the person writing the statment understands what the cause to STJ pronation will be on the STJ axis location.
Given that part of the point of notes is for the benefit of other professionals, if overpronation is a dx if the writer understands that it will cause a functional deviation of the axis, would it not be more accurate to write "functional deviation of the Sub talar axis"?

Regards
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Old 29th October 2009, 04:38 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
Originally Posted by m weber View Post
Overpronation is a diagnosis as long at the person writing the statment understands what the cause to STJ pronation will be on the STJ axis location.
Hi Michael,

I would have to disagree with this. In my opinion overpronation is not a diagnosis and should never be written (or spoken) as such. Even if it is terminology that a clinician is using and/or writing down - at best it can be described as an 'observation' rather than a diagnosis.

Oxford Dictionary definition of diagnosis:

Quote:
noun (pl. diagnoses) The identification of the nature of an illness or other problem by examination of the symptoms.
Ian
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Old 29th October 2009, 04:47 AM
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Default Re: Biomechanics Corner - Overpronation

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Originally Posted by Robertisaacs View Post
Only if people write to the journal, which I would encourage anyone to do!



Bless yew kind sir!. I'd hoped somebody would!

I'm between patients (damn them) so i'll kick off with a quick one.




What is the defining characteristic of "too much"? Is a matter of degrees or whether the foot has a pathology.



Given that part of the point of notes is for the benefit of other professionals, if overpronation is a dx if the writer understands that it will cause a functional deviation of the axis, would it not be more accurate to write "functional deviation of the Sub talar axis"?

Regards
1 too much pronation = pain, familar history of problems tripping history

2 To come back to with a question. How do you know the STJ axis is deviated ? How do you know that the deviation is the cause of the problems ? How do you measure the flow on effect of this deviation ? in Newton´s ?
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Old 29th October 2009, 04:51 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
Originally Posted by m weber View Post
Both the medial deviation and the attempt to resupinate ( lateral deviate the axis ) can lead to pathological complaints.
Yes, but that's the point - it can but doesn't necessarily.

Quote:
Originally Posted by Robertisaacs View Post
would it not be more accurate to write "functional deviation of the Sub talar axis"?
Yes, or maybe pathological deviation of the sub talar axis - but can't quite see that being confidently written on any referral

Quote:
Originally Posted by Ian View Post
at best it can be described as an 'observation' rather than a diagnosis.
I have to agree -

Last edited by Ella Hurrell : 29th October 2009 at 04:52 AM. Reason: typo
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Old 29th October 2009, 04:53 AM
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Default Re: Biomechanics Corner - Overpronation

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Originally Posted by Ian View Post
Hi Michael,

I would have to disagree with this. In my opinion overpronation is not a diagnosis and should never be written (or spoken) as such. Even if it is terminology that a clinician is using and/or writing down - at best it can be described as an 'observation' rather than a diagnosis.

Oxford Dictionary definition of diagnosis:



Ian
Therefore so is medially deviated axis an observation. Say we take PTTD Diagnosis, the casue we might write medial deviated STJ axis or STJ pronation or whatever it is still just an observation.


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Old 29th October 2009, 04:55 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
Originally Posted by m weber View Post
1 too much pronation = pain
No. Think causation.

Quote:
Originally Posted by m weber View Post
2 To come back to with a question. How do you know the STJ axis is deviated ? How do you know that the deviation is the cause of the problems ? How do you measure the flow on effect of this deviation ? in Newton´s ?
As above - how do you know 'overpronation' is the cause of the problems (pain)?
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Old 29th October 2009, 04:59 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
Originally Posted by m weber View Post
Therefore so is medially deviated axis an observation. Say we take PTTD Diagnosis, the casue we might write medial deviated STJ axis or STJ pronation or whatever it is still just an observation.
I agree - medially deviated STJ axis/STJ pronation moments are just observations also, and in your example the diagnosis is PTTD.

What you said was that 'overpronation' was a diagnosis. It's not.
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Old 29th October 2009, 05:02 AM
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Default Re: Biomechanics Corner - Overpronation

[quote=Ella Hurrell;117009]Yes, but that's the point - it can but doesn't necessarily.

Any medial or lateral deviation of the stj axis does not have to lead to pathological complaints. It is normal during CKC for there to be a change in the position of the axis both medially and laterally.

Say we take unstable ground which the GRF cause an external supination moment in the STJ the axis deviates laterally loading the PL,PB PT muscles this does not mean that there will automatically be a problem if the muscle are strong enough .

How this for a statement then A medial deviated axis in a child may over time lead to a more lateral deviated axis in that person in 10 years.
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Old 29th October 2009, 05:07 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
Originally Posted by Ian View Post
I agree - medially deviated STJ axis/STJ pronation moments are just observations also, and in your example the diagnosis is PTTD.

What you said was that 'overpronation' was a diagnosis. It's not.
If we agree then Robert and Ella would be wrong for writing functional deviation of the Sub talar axis an so would many people who think in the new school way of biomechanics and therefore when Robert sees ´medially deviated STJ axis ´on a form he should get just as red hulk like. ( But I guess he might smile if he read that)
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Old 29th October 2009, 05:19 AM
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Default Re: Biomechanics Corner - Overpronation

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If we agree then Robert and Ella would be wrong for writing functional deviation of the Sub talar axis
Fair point - I actually agree too - Diagnosis would be whatever condition it's leading to (PTTD to use your example).... although I did actually suggest pathological deviation, I concede that this is also an observation not diagnosis.
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Old 29th October 2009, 06:14 AM
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Default Re: Biomechanics Corner - Overpronation

Alright then say that the head of the NHS Forms section is reading this Thread.

They think we should have a cause or under lying pathology section on the form for referrals to Podiatrists.

Standard name etc blah blah

Diagnosis PTTD Cause excessive pronation/ overpronation

How red Hulk are you guys now ?
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Old 29th October 2009, 06:46 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
If we agree then Robert and Ella would be wrong for writing functional deviation of the Sub talar axis
Nope. Never said that that should be the diagnosis. I said that if you are writing overpronation on the basis that it causes a deviation of the axis, and that it is the deviation which causes the pathological forces, that you should write what you mean.

Quote:
Diagnosis PTTD Cause excessive pronation/ overpronation
I'd be puce if I didn't know that you were playing devils advocate.

To come back to what you said earlier (how fast is this thread moving?!)

Quote:
1 too much pronation = pain
This is what I alluded to in the article because this is where the definition of overpronation becomes tautological and I think this tautology creates a fallacious logic loop which has misinformed a generation of biomechanics.

We agree that we cannot define a threshold for a normal amount of pronation. So you define overpronation by enough pronation to cause pain.

Its a given that most people in RSCP will be pronated more than neutral.

Its a given that most people who come to see a podiatrist for a biomech assessment have pain.

Therefore, we have pain, and we have pronation in most patients we see. So the diagnosis of overpronation becomes inevitable for any patients who are not pathologically supinated, simply because they have pain and pronation to some degree.
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To answer a point which came up in a few emails.

We all see patients who come in with their nav's resting on the ground, their knees facing each etc etc. That is often pathological for assorted reasons including the axial position. Is this not "overpronated"?

Well, kind of, however, is it good practice to refer to these as "overpronated"? When another clinician reads your notes how do they know that the feet were pes pancakeus as opposed to pronated a few degrees from neutral... but causing pain (as per the definition above).

Does "overpronation" tell us that the rscp is thus, or does it reflect gait? Does it tell us the supination resistance? Whether the person is hypotonic or has ligamentous laxity; or both, or neither? Does it tell us if the deltoid ligament complex has been stretched? Does it tell us which structure is limiting the pronatory range, and when? Does it tell us the position of the foot at heel strike, mid stance or toe off? Does it tell us that the axis is functionally deviated because of the position of the joint within its range at a certain point or whether the whole bundle is deviated? Does it refer to the overall range or the amount of it which is used?

It tells us nothing, save that there is A: pain and B: some unspecified degree of pronation beyond neutral. Which most patients have.

Lets get down to cases and take two patients.

One is a 6 year old with downs syndrome. They are hypotonic, have gross ligamentous laxity and excessive available range in the STJ and TC joints. When they stand their arch dissappears completely and the lateral side of their foot actually lifts from the ground.

They, by conventional definition, are "overpronating".

The other is 67 years old and has just had bunion surgery which stuffed up her windlass mechanism. As such the deltoid ligament has more to do to limit joint motion when they heel lift and has started to be a bit painful. Their feet operate in a range between 2 degrees from neutral and 8 degrees from neutral, even when in RSCP their arch is 13mm from the ground. But they are getting pain associated with pronation.

They, by conventional definition, are also "overpronating".

How can a term which covers such radically different pathological functions be even remotely informative or useful in notes?

Kind regards
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Old 29th October 2009, 06:53 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
Originally Posted by m weber View Post

Any medial or lateral deviation of the stj axis does not have to lead to pathological complaints. It is normal during CKC for there to be a change in the position of the axis both medially and laterally.

Say we take unstable ground which the GRF cause an external supination moment in the STJ the axis deviates laterally loading the PL,PB PT muscles this does not mean that there will automatically be a problem if the muscle are strong enough .

How this for a statement then A medial deviated axis in a child may over time lead to a more lateral deviated axis in that person in 10 years.
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Originally Posted by m weber View Post
If we agree then Robert and Ella would be wrong for writing functional deviation of the Sub talar axis an so would many people who think in the new school way of biomechanics and therefore when Robert sees ´medially deviated STJ axis ´on a form he should get just as red hulk like. ( But I guess he might smile if he read that)
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Originally Posted by m weber View Post
Alright then say that the head of the NHS Forms section is reading this Thread.

They think we should have a cause or under lying pathology section on the form for referrals to Podiatrists.

Standard name etc blah blah

Diagnosis PTTD Cause excessive pronation/ overpronation

How red Hulk are you guys now ?
Michael all of your posts are confusing me - I know you are playing devils advocate but I am not entirely sure of the point you are making/arguing?

As for this:

Quote:
Originally Posted by m weber View Post
Diagnosis PTTD Cause excessive pronation/ overpronation
Rob let it go, but I'll say it again - think causation. How can one state the above confidently on a form? How does one not know that instead of the 'overpronation' causing the PTTD, that infact the PTTD did not cause the 'overpronation'?
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Old 29th October 2009, 06:56 AM
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Default Re: Biomechanics Corner - Overpronation

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Its a given that most people in RSCP will be pronated more than neutral.

Its a given that most people who come to see a podiatrist for a biomech assessment have pain.

Therefore, we have pain, and we have pronation in most patients we see. So the diagnosis of overpronation becomes inevitable for any patients who are not pathologically supinated, simply because they have pain and pronation to some degree.
Pronation the movement does not always lead to pain. Pain the the bodies way of explaining that the movement of pronation andor attempting to stop it is too much...... therefore without taking out my goniometer Ive noted that I need to stop pronation for my tx plan because there is overpronation.
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Old 29th October 2009, 07:09 AM
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Default Re: Biomechanics Corner - Overpronation

Ian and Robert etc.

I guess some of what I´m trying to argue is that ... if we can not say overpronation then we can not say medially deviated axis for many of the same reasons.

I think that this is some of the main issues with people is that they read the 1st lines of the papers written on this stuff and think that what was excessive pronation now become Medially deviated axis and off they go which means that they are in this never never land where is just does not make sense.

My brain may over heat here it´s very hard to argue for something that you don´t beleive in. I´ll continue but it may get more confusing and when the thread is done a might have to slip in a disclaimer " I don´t beleive what I argued for in this thread "
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Old 29th October 2009, 07:32 AM
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Default Re: Biomechanics Corner - Overpronation

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I guess some of what I´m trying to argue is that ... if we can not say overpronation then we can not say medially deviated axis for many of the same reasons.
No, I disagree, we can say it - so long (and perhaps this is harping on again) as it's recognised that this is also an OBSERVATION that is NOT necessarily a cause. The whole concept of causation is not clearly understood by many, evidently - just look at MMR/Autism, Swine Flu jabs/GBS....

Quote:
I think that this is some of the main issues with people is that they read the 1st lines of the papers written on this stuff and think that what was excessive pronation now become Medially deviated axis and off they go which means that they are in this never never land where is just does not make sense.
Exactly - you have just argued yourself around in a circle??!

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when the thread is done a might have to slip in a disclaimer " I don´t beleive what I argued for in this thread "
So give it up mate. Now.
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Old 29th October 2009, 07:43 AM
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Default Re: Biomechanics Corner - Overpronation

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Originally Posted by Ella Hurrell View Post
No, I disagree, we can say it - so long (and perhaps this is harping on again) as it's recognised that this is also an OBSERVATION that is NOT necessarily a cause. :
Ok Ella the observation and cause thing is covered we all agree

I want you picture a classic pes planus foot type in RCSP Navicular close to the ground etc.

Think 10 years ago you might have discribed in your journal "foot overpronated"

Now think today what would you write in your Journal
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Old 29th October 2009, 08:22 AM
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Default Re: Biomechanics Corner - Overpronation

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So give it up mate. Now.
No DON'T! Whether or not the views expressed are that of the author, they are certainly very commonly held views! Without someone who will voice them, those who are following this thread but reluctant to post should be able to learn something from the exchange!

Tell you what. Tomorrow I will argue FOR overpronation as a valid assessment observation and you can argue against.

Quote:
I guess some of what I´m trying to argue is that ... if we can not say overpronation then we can not say medially deviated axis for many of the same reasons.
Nah. Not buying. Overpronation can cover any of the factors I listed here

Quote:
Does "overpronation" tell us that the rscp is thus, or does it reflect gait? Does it tell us the supination resistance? Whether the person is hypotonic or has ligamentous laxity; or both, or neither? Does it tell us if the deltoid ligament complex has been stretched? Does it tell us which structure is limiting the pronatory range, and when? Does it tell us the position of the foot at heel strike, mid stance or toe off? Does it tell us that the axis is functionally deviated because of the position of the joint within its range at a certain point or whether the whole bundle is deviated? Does it refer to the overall range or the amount of it which is used?
and more.

Leave alone that its tautological, it just does not give any useful information! Whereas "medially deviated axis" could refer to the position of the bundle of axis, or the position of the axis within the bundle, but it is a pretty open and shut observation. And if I see it in the NWB part of someone elses assessment I know that it refers to the position of the axial shadow with the foot in paralel plantar position.

Regards
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Old 29th October 2009, 08:46 AM
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Default Re: Biomechanics Corner - Overpronation

Allright I see was Ella says later.......

Medially deviated from what ? What is the normal position of the STJ axis ?

Overpronated indicates a static position where the calc is everted talus .... etc this will also cause strain on the detoid ligament complex due to the change in position of the talus. calc navicular etc.

Quote:
Does "overpronation" tell us that the rscp is thus, or does it reflect gait? Does it tell us the supination resistance? Whether the person is hypotonic or has ligamentous laxity; or both, or neither? Does it tell us if the deltoid ligament complex has been stretched? Does it tell us which structure is limiting the pronatory range, and when? Does it tell us the position of the foot at heel strike, mid stance or toe off? Does it tell us that the axis is functionally deviated because of the position of the joint within its range at a certain point or whether the whole bundle is deviated? Does it refer to the overall range or the amount of it which is used?
No it does not but writing Medially deviated stj axis will not also.

We can by using words like overpronated at toe off.
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Old 29th October 2009, 09:18 AM
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Default Re: Biomechanics Corner - Overpronation

Robert:

You have created another beast of a thread....good job!

There are many valuable lessons to be learned here in this thread. First of all, we must understand that "pes planus deformity" or "pes plano valgus deformity" or "pes valgus deformity" are acceptable diagnoses and are commonly used. I use them commonly in my charts since my charts need to read by insurance company representatives and non-podiatric health professionals who would not know what a "medially deviated subtalar joint axis" is. However, the term "overpronation" is not a diagnosis and should never be used as a diagnosis.

One must remember when we speak of the subtalar joint (STJ) there are two very important parameters which are quite distinct from each other, but interrelated. The STJ axis spatial location is the 3D location of the STJ axis relative to the plantar foot (e.g. medially deviated, laterally deviated). On the other hand, the STJ rotational position refers to where the STJ is within its rotational motion (e.g. maximally pronated, neutral position, maximally supinated, 2 degrees from maximally pronated, etc). As the STJ rotates in a pronation direction, the STJ becomes more medially located relative to the plantar foot. As the STJ rotates in a supination direction, the STJ becomes more laterally located relative to the plantar foot.

Therefore, when we see a child with a significant pes plano valgus deformity, their STJ will be maximally pronated in stance (i.e. STJ rotational position) and their STJ axis will be medially deviated (i.e. STJ spatial location). Both of these STJ parameters should be noted by the clinician since they tell us where the STJ is within its range of motion during stance and where the STJ axis lies in space so that we can make an estimate of which of the structural components within their foot and lower extremity will be subjected to possibly pathological levels of stresses during weightbearing activities.

However, there are cases, such as in patients with high degrees of rearfoot varus deformity, limited range of STJ motion and metatarsus adductus deformity, where things are not so clear. In these feet during standing, their calcaneus will be inverted but also their STJ will be maximally pronated. These feet, even though not common, may experience supination instability and peroneal tendon pathologies even though they are maximally pronated at the STJ (or as some would say, "overpronated").

The biomechanical cause for their STJ supination instability and peroneal tendon pathologies are not due to "overpronation" but rather due to their more lateral STJ spatial location since the plantar calcaneus is so medial to the STJ axis (i.e. calcaneus is so inverted) and Achilles tendon insertion is so medial to the STJ axis. In these feet, they are both maximally pronated at the STJ and experience "oversupination" pathologies of supination instability and peroneal tendinopathy. This is why it is so important for the more advanced clinician to fully understand the kinetic effects of STJ axis spatial location and how both the external STJ moments from ground reaction force and internal STJ moments from joint compression and central nervous system controlled muscular activity all interact together to produce both motion and stability at the STJ.
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Old 29th October 2009, 09:24 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
Medially deviated from what ? What is the normal position of the STJ axis ?
Fair comment. My assessment form actually has lil pictures of feet upon which I draw the position of the axial shadow when the foot is in parallel plantar. A simple descriptive of "medially deviated axis" is not particularly informative.

Quote:
Overpronated indicates a static position where the calc is everted talus .... etc
Overpronated is any position where the calc is everted? That means ANY pronation is OVER pronation. It does not tell me anything which does not apply to 90% or more patients.

Anyway you said earlier that "too much pronation = pain,". Which is it, pronation in the presence of pain or everted calc? And how can it be a meaningful observation if everyone has such radically different ideas of what it means?

Quote:
this will also cause strain on the detoid ligament complex due to the change in position of the talus. calc navicular etc.
Is that not what the deltoid ligament is there for? What happens to ligaments upon which no strain is placed?


Quote:
We can by using words like overpronated at toe off.
Nope. Because this patient

Quote:
One is a 6 year old with downs syndrome. They are hypotonic, have gross ligamentous laxity and excessive available range in the STJ and TC joints. When they stand their arch dissappears completely and the lateral side of their foot actually lifts from the ground.
Could be described as overpronated at toe off, as could this one

Quote:
The other is 67 years old and has just had bunion surgery which stuffed up her windlass mechanism. As such the deltoid ligament has more to do to limit joint motion when they heel lift and has started to be a bit painful. Their feet operate in a range between 2 degrees from neutral and 8 degrees from neutral, even when in RSCP their arch is 13mm from the ground. But they are getting pain associated with pronation.
And they are nothing alike.

Mid stance overpronation could cover anything from a stiff arthritic foot with a pronatory range of 6 degree and DCIS through the aforementioned massively hypermobile downs kiddie, and indeed a CP kiddie with a tight Triceps Surae and a massive amount of escape pronation.

They could all have pain in the presence of pronation.

They all pronate (overpronate).

Yet they are radically different problems with radically different causes and require radically different management!

Regards
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Old 29th October 2009, 09:41 AM
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Default Re: Biomechanics Corner - Overpronation

Quote:
You have created another beast of a thread....good job!
Call me baron Frankenstein. I cobbled it together from bits of many dead threads then stuck a bolt of lightening through it. Hey presto, the monster lurches off toward the village leaving me with a slight concern as to whether I put the knees on the right way around.

Its slightly peripheral, but I thought I'd poke this little gem in from a UK podiatrist website

Quote:
If your ankles roll out (supinate) when you walk or run, and there is no structural reason for it, you are an over-pronator (hyperpronator) in disguise.
So supinators are overpronators too! But in disguise...


Acme Supinator kit

Cheers
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