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Foot orthotics - allow pronation at heel strike?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Conradm, Jul 20, 2010.

  1. Conradm

    Conradm Member

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    In construcion of foot orthotics: How much pronation is it necessary to allow for at heel strike? Either with orthotic flex or an angle ground on the heel post. I know maybe I am oversimplifying the issues at hand, but as I understand it totally rigid control of the foot - while maybe not the worst - is best avoided...

    Anyone have any input or discussions or documents they could link me to?
  2. Re: foot orthotics - allowed pronation at heel strike

    Depends on what your trying to achieve with your device and what tissue your attempting to reduce the stress on.

    So sometimes you want the foot to pronate as quickly as possible after heel strike other times as little as possible- so depends and what you want the device to do.
  3. Phil Wells

    Phil Wells Active Member

    Re: foot orthotics - allowed pronation at heel strike

    Depends on the stiffness of the sole unit of the shoe. Leather soles do not compress, spongy heels do = allow for varying amounts of shoe compression when allowing for any movement.

  4. Conradm

    Conradm Member

    Re: foot orthotics - allowed pronation at heel strike

    OK...for the sake of discussion
    29 yr old patient, left foot plantar fasciitis secondary to pronation (bilateral)
    doctor has prescribed for custom orthotic with deep heel cup. He wears fairly generic work boots most of the day.
  5. Re: foot orthotics - allowed pronation at heel strike


    And indeed more or less completely impossible. Actually no, strike that, Completely impossible. Even a SMAFO allows a certain amount of "slop".

    How much tension is there on the plantar fascia at heel strike?
  6. Re: foot orthotics - allowed pronation at heel strike

    Ok. I'm told I may be being unfriendly. I'll try again with my happy face on.

    Hey Conrad, welcome to the arena :welcome:.

    You raise an interesting question. However I fear that there can be no simple answer as the question presupposes several things which are not neccessarily workable even in the abstract.

    One cannot "control" the amount of pronation at heel strike. At the instant of heel strike GRF (ground reaction force) has not really started working yet and as this is the means by which othoses operate, we cannot really affect this very much.

    2. Even when the heel is loaded, research shows that there is a wide variance in the kinamatic effect of an insole, Viz, how much change it makes to calc position. A 5 degree rearfoot post may make one foot invert by 3 degrees, another by no degrees, or even make a foot evert. Therefore we cannot really talk about how much pronation we allow because we are not really in control of it.

    3. Assuming that as you say the plantar fascitis is caused by pronation (winces slightly) the amount of pronation at heel strike may not be the most significant. Pronation causes 1st ray dorsiflexion moment, the Plantar fascia limits it by causeing 1st ray plantarflexion moment. The tension in the Plantar fascia therefore does not peak until the forefoot is loaded.

    4. Its not really ideal to talk about PF being "caused by pronation". Most everybody pronates, the lack thereof is pathological. Therefore the confluence of PF and pronation cannot really be said to be a causal link. One might as well say a patient has PF because they have a head, because everyone with PF has a head.

    So I'm afraid you may not find a simple answer to your question because there is no simple answer.

    If you were looking for specific prescription advice more information would be helpful, are you that 29 year old?
  7. Conradm

    Conradm Member

    Re: foot orthotics - allowed pronation at heel strike

    no worries. People who are always really freindly can get abnoxious.
    I know -- my question was very general in nature. No I am not the 29 year old.

    I am a Pedorthist and manufacture orthotics for patient referred to me by several different MD's and PT's. So far I treat each case entirely seperate, but was wondering if there was any guidelines or "rule of thumb" for this issue.

    So I guess getting a simple answer would have been nice but I was not fully expecting one.


    I have no actual measurments, but at 85kg, with >15cm of vertical travel and arch height (scale of 5) goes from 4 non-wt down to 1 RCSP...

    thanks for the input
  8. Re: foot orthotics - allowed pronation at heel strike

    I resent that. How DARE you suggest that I am always friendly?:mad:;)

    Might be a terminology thing but I'm afraid you've lost me here. Do you mean the foot travels down 15 cms from the peak of its swing to the ground?

    So far as the arch lowering, I'm afraid I'm gonna get complex on you again.

    1. The arch lowering you descibe does not happen at heel strike. After heel strike, perhaps.

    2. The degree to which the arch height drops may have little bearing on the tension in the PF. Consider two ropes one short, one long, tied to two identical stones. The tension in the rope when they come to rest is the same.

    3. A much more significant element in how much PF tension there is might be what other structures are contibuting to arresting pronation / arch drop. For eg, consider two identical arches, 4 to 1 as you describe. One has a hugely floppy 1st ray, the other a stiff 1st ray. The arch height is the same, but the PF tension will be higher in the floppy 1st ray because all the tension is taken in the PF and much less in the ligaments around the 1st met.

  9. Conradm

    Conradm Member

    Re: foot orthotics - allowed pronation at heel strike

    the 15cm bit was the distance his HAT(Head Arms Trunk) travel vertically throught the gait cycle. I'm bad with names and terminology mostly...sorry. And being just a pedorthist am only supposed to be able to generally verify the physicians diagnoses or prescription...Biomechanics fascinates me though and I hate only knowing something halfway.

    I follow you on the PF tension though. And maybe I should have said hyperpronation and moderate-severe FnHL...

    ...maybe the horse is dead now...:deadhorse:
    I'm learning though:cool:
  10. Re: foot orthotics - allowed pronation at heel strike

    I think somethings on fire in Kent, no it´s just the smoke coming out of Roberts ears.

    Conrad the term Hyperpronation maybe the same as saying to your best mate you just slept with his younger sister, Just not the done thing.

    FnhL will have a role to play in tension within the plantar fascia. What I would suggest is taking the time to read through the threads in the biomechanics forum, there will be tons of infomation for you to read about.

  11. Conradm

    Conradm Member

    Re: foot orthotics - allowed pronation at heel strike

    fair enough...
  12. Re: foot orthotics - allowed pronation at heel strike

    And when you've finished reading all of that, give your patient a prefabricated foot orthosis as the best available evidence suggests that this will be as equally efficacious as a custom device.

    Welcome to the show.:bash:
  13. Griff

    Griff Moderator

    Re: foot orthotics - allowed pronation at heel strike

  14. Re: foot orthotics - allowed pronation at heel strike

    Conrad, if you give us all the information you have on your patient. We can try to give you some advice, or ask more questions and/or send you off for more reading.

    So we have an 85 kg with Left side Plantar fasciitis.

    FnHL - sever to moderate ( probabely best described as having increased dorsiflexion stiffness of the 1st)

    Arch height decreased from 4 out of 5 to 1 in midstance ( I guess this is navicular drop)

    What other info have you got for us ?

    A few questions - how long have the patient had the pain, what other treatment besides the orthotic your providing is the patient on.

    What type of device had you thought to prescribe?
  15. Re: foot orthotics - allowed pronation at heel strike

    lalalalalalala I'm humming a tune, I can't hear you :mad:

    I'm going to disagree with you there!

    If Conrad is choosing now, between a standard Root custom cast and a pre fab, then yes, he may as well use a pre fab.

    But when he's "read all of that", he'll have ended up with a broader knowledge of the specifics of pathology and function. There is no study comparing the efficacy of THAT against a pre fab. So although we cannot confidently say that this WILL perfom better, it is not true to say that the evidence suggests that a custom device based on a full choice and knowledge of models and materials is equal to a pre fab. THAT study has not been carried out.

    IMO ;)
  16. Conradm

    Conradm Member

    Re: foot orthotics - allowed pronation at heel strike

    Patient had symptoms for 3 months before I saw him.
    Hallus dorsiflex >60 deg non-wt, 0 deg when standing.

    The prescription was for a custom orthotic with deep heel cup, which I made using a 3mm subortholen shell posted with cork. He complained the "arch was too high" so I filled the arch on plaster cast and re-formed. Patient says he is happy but has had no follow up yet.

    I started wondering if the initial device had been unsucessful because it was too rigid a conrol at heel strike...hence my initial question.

    It puzzle me that such a device relieved the symptoms (no heel lift by the way) But it is just what the doctor ordered.
    thanks again
    - Conrad
  17. Conradm

    Conradm Member

    Re: foot orthotics - allowed pronation at heel strike

    I am busy reading...but...
    If you don't use the term *****pronation (I didn't make that one up!) for someone who walks like a duck. What do would you call it?
  18. Re: foot orthotics - allowed pronation at heel strike

    So, forget that my tongue was in my cheek, what does the best published evidence tell us, Robert? Here's what my anecdotal tells me, there are very few cases of plantar fasciitis that I have seen, and I see about a dozen a week, that haven't cleared up with a pre-fab- shocking news just in. My weapon of choice- Vasyli Dananberg. What are the features you would you put into a custom device designed to treat plantar fasciitis which are not found in this prefab?
  19. Re: foot orthotics - allowed pronation at heel strike


    It could have been that your higher shelled device was causing irratation to the Plantarfascia.

    Alot of us try and talk in terms of moments,force, load on tissue.

    so in your case- plantar fascia pain - tension in the plantar fascia and then once thats been decided on look at the forces which are causing the tension in the plantar fascia and build a treatment plan around that.

    heres some more reading for on the windlass mechanism- http://www.podiatry-arena.com/podiatry-forum/tags/index.php?tag=/windlass-mechanism/
  20. Re: foot orthotics - allowed pronation at heel strike


    I can't agree with one or two of the things you stated here:

    We can control the amount of pronation that occurs immediately after heel strike during the contact phase of gait with a specially designed foot orthosis and/or shoegear modifications. In addition, by definition, GRF starts working at the instant of heel strike and also begins to cause external moments to be generated across the STJ at the instant of heel strike. Therefore, we can affect very much during the contact phase of gait....if we choose to do so with our orthosis design or shoe modifications.

    In addition, pronation can be a cause of plantar fasciitis, but so can many other factors. But, like you, I hate the term "hyperpronation". Why not just say excessive pronation during a certain phase of gait (i.e. contact phase, early midstance phase, late midstance phase, propulsive phase) and I think everyone will understand what is being said.
  21. Re: foot orthotics - allowed pronation at heel strike

    We'll have to agree to differ here Kevin. Of course I would agree that we can affect the degree of pronation. And yes grf starts acting at heel strike and affects the kinematics through the contact phase.
    But if there is one thing you yourself have taught me it's the importance of good terminology.

    To me, to "control" pronation implies that we have control as to the amount of pronation. Do we? For a given foot, could we design an orthotic which will acheive a certain number of degrees kinematic change? Can we predict exactly the kinematic effect our device will have? I can't. I can confidently say my insole will exert supination moment, where it will exert it's grf, to an approximate degree the vector of the force. I can't predict the amount of kinematic change which will result in vivo. For that reason I don't think we can "control" pronation.

    At the risk of being predictable, it depends. For many cases of pf I too use a prefab (I prefer the interpods modular but that is by the by). However if there is a gross variation then the modification will be worked around to that.
  22. Re: foot orthotics - allowed pronation at heel strike

    I'll forgive you. I know that over / uber / hyper / mega pronation are not you're fault. It's one of my pet peeves.

    There is an article I wrote on the subject here


    But in broad strokes, I don't like it because it tells me nothing of value.

    Overpronation has no specific definition. If someone says overpronation they might mean any of the following.

    Pronation happening too soon.

    Pronation happening too fast (velocity)

    pronation happening too long (duration) for eg of the windlass is bust and the foot does not resupinate

    mid stance pronation to an excessive degree (whatever that degree is)

    Pronation beyond the tissue stress threshold or anatomical tolerance of the patients ( for eg an ra patient for whom 10 degrees pronation is too much)

    pronation considered excessive because of an injury rather than degree or timing.

    It does NOT tell me

    Why the foot is doing whatever it is doing.

    What structural compensations there are (if any)

    What supination structure (if any) is incompetant.


    So if you say someone is over pronated they could be any of the following

    fixed rigid pes planus caused by a non correctable supinatus
    globally hypermobile correctable squashy foot in which all the joints have excessive range and little stiffness

    a foot with a surgically shortenened 1st ray

    a foot with a medially deviated axis making it structurally sound but functionally unstable because the pronation moments are amplified.

    Etc etc.

    You see my frustration? To me overpronation is like "headache". It Tells us little about what is actually happening and, like headache, the treatment depends on the type. A rigid flat foot and a hypermobile hypotonic kiddie foot are both overpronated but you would not dream of treating the same
  23. Re: foot orthotics - allowed pronation at heel strike

    We showed orthotic effects on CoP position during loading response (0-10%) stance.

    Attached Files:

  24. Re: foot orthotics - allowed pronation at heel strike


    I believe the word "control" is a word that very well describes our ability to modify ground reaction forces and produce kinematic changes with foot orthoses. Some foot orthoses have little to no control, other orthoses have very good control.

    Control: Power to direct or determine

    Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992.

    By the way, just because a heel wedge or one design of foot orthosis doesn't decelerate pronation of the subtalar joint during contact phase doesn't mean that a larger heel wedge or a better designed foot orthosis can't exert control over subtalar joint pronation during contact phase.
  25. Conradm

    Conradm Member

    Re: foot orthotics - allowed pronation at heel strike

    So is it safe to say that - without specific purpose - pronation contol at heel strike is an over-promoted (maybe I should say hyperpromoted?) concept?

    It's safe to swim
    in Pemrose Park
    I guarantee
    There are no Sharks
    - Shel Silverstein

  26. joejared

    joejared Active Member

    Re: foot orthotics - allowed pronation at heel strike

    If one wants to encourage pronation at heel strike, it would seem that the shoe, rather than the orthotic should have this pronation ground into the proximal edge of the shoe. As to the moment after heel contact, it can be encouraged to whatever degree, simply by the definition of the grindoff area. Commonly, the grindoff area is relatively small compared to the surface area of the heel post, but I've filled requests for much more dramatic areas, covering as much as 50% of the heel post. "Control" is probably too extreme of a term for most devices I've seen, but it is possible, assuming the surface below the orthosis is not so mushy that the heel post is restricted from rotating in the shoe.
  27. Re: foot orthotics - allowed pronation at heel strike

    I guess the devil is in the detail. Do we mean direct or do we mean determine.

    Direct? I'd agree with that. Notwithstanding those pesky rogue data points we can generally send the foot one way or other.

    Determine? I remain to be convinced that anyone can make an orthotic which will determine the amount of pronation which takes place , or when, with any degree of repeatability.

    To me, control implies a greater degree of control than we have. I control my car, meaning I decide exactly which way it goes. If I get a flat tire it certainly pulls my car one way, directs it if you will, but it does not control where it goes, it just shoves it in one direction.

    I think it depends which definition of control you mean ;)

    Honest question. Can the better design of orthotic determine the position and timing of the STJ during contact phase. If I showed you a foot with a maximally pronated position of, say, 8 degrees calc eversion at 30% of stance, can we give an orthotic which will reduce that position at that time to 3 degrees? Simons study showed we can reasonably predicatably affect COP position, does that extrapolate to predictable kinematic position?
  28. Re: foot orthotics - allowed pronation at heel strike

    No. Nor does it extrapolate to change in moment. I don't know why Joe thinks the grind-off needs to be at shoe-ground interface as oppose to the orthosis-shoe interface either?

    Personally, I've never once added any grind off to any of my orthoses.
  29. Re: foot orthotics - allowed pronation at heel strike

    Oh and

    There IS science to biomechanics to be sure. But there is a long history of people exaggerating what is known, and presenting simplifications as facts. And that is the problem because when a simplified clinical model is represented as a firm scientific fact, extrapolations are made from it and the science goes off on an unhelpful tangent.

    Case in point, "classic" Root theory. As a pure clinical model, a suggestion of what to do and when, one could do a lot worse. Certainly its never been shown to be exceeded as a model, inductive evidence wise.

    But as a scientific model, normal is not normal and much of it has never been validated. Which is fine if thats accepted as such. But others, post root, have misrepresented his model as more than it was ever intended to be and that has led to some of the egregious errors we see in the science today.

    For example. Sub talar neutral was described in root as the position neither supinated nor pronated. Others since have claimed that this means its the "right" position and that the foot should be held in neutral throughout stance. Root never said that, and it makes little sense. Thats what you get when a clinical recommendation (cast the foot in neutral) is re-interpreted as a scientific reality (the foot should function in neutral).

    So yes, perhaps pronation control at heels strike is "hyperpromoted" (love it).
  30. joejared

    joejared Active Member

    Re: foot orthotics - allowed pronation at heel strike

    The only reason for that input is that validly it was suggested that at heel strike contact there is no encouragement towards pronation that a standard orthosis could maintain at that point, short of possibly a modified kinetic wedge. I have noticed that not all shoes with a chamfered or rounded heel strike zones are perpendicular to the calcaneus.

    Not surprising, many practitioners simply ask that the rearfoot match the forefoot.

    In shoe, and once full heel contact is made, motion within the orthosis could be either allowed for or encouraged, depending on how much of the heel post surface area is used for motion grindoff.
  31. Re: foot orthotics - allowed pronation at heel strike

    Joe, I have tried to make sense of what you have written here, but to me at least it makes no sense at all.

    And again??????
    I'm trying to think of a study which has looked at rearoot motion in feet with orthosis in situ, which demonstrates that the amount/ timing of rearfoot eversion is influenced by a grind-off. Do you know what, I can't think of any. I'll put my head on the block and say this again, grinding motion into posts is utter nonsense- think about it.

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