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Biomechanics and foot orthoses

Discussion in 'Biomechanics, Sports and Foot orthoses' started by biomech, Jun 29, 2006.

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  1. biomech

    biomech Member

    Members do not see these Ads. Sign Up.
    Alot has been said about the effectiveness of foot orthoses.

    Has anyone got any research papers or references on exactly HOW the orthoses work.

    It seems that "for every degree of pronation at the STJt there is an equal amount of internel rotation of the tibia" which causes a genu valgum, LLD etc etc has gone out of fashion.

    I need articles on what the orthoses does and what effect it has on posture.

    Please help.

  2. I would suggest a good starting point would be to read the list of references Prof. Kirby listed in the skives and posts thread.
  3. Craig Payne

    Craig Payne Moderator

    There is only one way foot orthotics work: They reduce stress in injured tissues.
    Where did you get that from? - it never been true. there is plenty of good data that says otherwise
  4. DaVinci

    DaVinci Well-Known Member

    One big thing I got from CP last weekend on how foot orthoses work was - they reduce forces! Its amazing how simple it can be. Why all the focus on degrees and angles and motion?
  5. Josh Burns

    Josh Burns Active Member

    Dear All,
    We know that the mechanism of custom orthotic therapy for the painful cavus foot is by reduction and redistribution of plantar pressure (Burns J, et al. Effective orthotic therapy for the painful cavus foot: A randomized controlled trial. JAPMA 2006;96:205-211.)

    Perhaps this mechanism is also true for the 'normal' and planus foot types? Redmond et al (2000) has shown that in individuals with 'excessive' pronation, foot orthoses also have the effect of reducing and redistributing plantar pressure (Effect of cast and noncast foot orthoses on plantar pressure and force during normal gait. JAMPA 2000;90:441-9). However, this improved plantar pressure distribution has not been shown to result in a reduction of patient symtoms in patients with excessive pronation (yet?).

    Joshua Burns
    NHMRC Australian Clinical Research Fellow
  6. Craig Payne

    Craig Payne Moderator

    We got a paper 'in press' at JAPMA that shows no correlation between between changes in the pattern of rearfoot motion and changes in patient symptoms. We also got some exciting data that preparing at the moment on failed orthoses in plantar fasciitis that surprising shows a very consistent and obvious change in some plantar pressure parameters in the orthoses that failed.... we live in exciting times...
  7. I need to disagree with you here, Craig. Foot orthoses do not only "work" by reducing "stress in injured tissues". Foot orthoses, more specifically and accurately, reduce the magnitude of pathological forces and/or stresses acting on selected structural components of the foot and lower extremity that are either currently injured or that may be currently uninjured to either try to heal current injuries or to prevent injuries from occurring in the future. Foot orthoses are also commonly used to improve performance in sports activities such as in alpine skiing and ice skating. Foot orthoses are commonly used likewise to improve the function of gait, such as in treating abnormal gait patterns in children and adults. I would agree that the major function of foot orthoses is to reduce stress in injured tissues, but to say that "there is only one way foot orthotics work: they reduce stress in injured tissues", would not be an accurate reflection of the multiple clinical uses and performance-enhancing capabilities of foot orthoses.
  8. Craig Payne

    Craig Payne Moderator

    Kevin - not sure we are disagreeing.

    This thread gives me a chance to raise something I was going to start a new one on....

    In the context of Karl's study (Effectiveness of Foot Orthoses to Treat Plantar Fasciitis) that showed no difference between prefabs and custom made for plantar fasciitis and comments made by Ed in the Skives & Posts thread and many other threads we have had ... what is the role of foot orthoses. I think we can agree on the altering force thing, but where I see a lot of disagreemnt that does happen is in the concept of:

    "Masking of symptoms" vs "biomechnical correction"

    Its obviously in the professions best interest to claim the prefabs "mask symptoms" and custom made achieve "biomechancial correction" -- but what really is "biomechanical correction"? I certainly do not think we can agree on what it is and there is certainly no evidence to say what it is. Is it really important to achieve "biomechanical correction" rather than "mask symptoms" .... to me this is where the "can of worms" lie...
  9. davidh

    davidh Podiatry Arena Veteran

    Good point Craig.
    Clearly biomechanical correction hails back to the bad old days when it was largely accepted that anything deviating from the "norm" (ie lower third of the leg perpendicular to the supporting surface and heel and mets in the same plane) was abnormal and needed "correcting".
    So is "biomechanical correction" an outmoded, and redundant concept?
    I say yes.

    Why fit devices?
    I believe (and I have to be careful what I write here!) that orthoses, whether custom or pre-form, do little more than provide an interface between the foot and shoe/supporting surface. They allow the foot to work a little more around STJ equilibrium position on those surfaces which may otherwise force the foot into constant and repeated pronation.
    My own preference for custom devices derives, not from the fact that they achieve "biomechanical correction", or even from profit motivation, but more from good customer service.
    Custom devices, in my experience, fit shoes better, last longer (with many labs now guarranteeing their devices for life), are much more resistant to dog-chew etc etc.

  10. biomech

    biomech Member

    Seems as though I have been too simplistic as the replies so far are just plain useless.

    A Pt arrives in the clinic with knee, hip, lower back and neck pain. You assess the gait, do your biomechanical assessment etc, I'm not going to go too far into this.

    You find that there is a bi-lateral HAV, genu valgum causing a LLD all on the left.
    Left hip 20mm lower than right, functional scoliosis and right shoulder 10mm lower than left.
    Pt complaining of shin splints on left, sciatica on right, left knee pain with crepitus and lower back pain, slight neck crepitus due to compensation, clicky jaw (one for you Rothbart), also headaches.

    I have dummy insoles in clinic with medial wedges so I used these and the genu valgum reduces, hips become equal aswell as shoulders (this is where the supination and external rotation of the tibia comes in Mr Aussie, BTW I was taught this at Uni and I feel its true whatever the research says, seen it too many times to dismiss it).

    Pt returns in 2 months and is pain free.

    I feel that the tibia has externally rotated reducing the genu valgum, this in turn has levelled the hips and therefore no need for functional scoliosis which has resolved the sciatica.
    Neck well, no need to compensate so inline with spine. Pelvis now in correct position so no kyphosis and jaw retracts to its normal position resolving clicking.

    Now forgetting redistribution of forces as if we are talking about resolving callus or corns, PF etc.

    POSTURALLY at every joint above the orthoses, WHAT IN YOUR OPINION DOES THE ORTHOSES DO.
    Forget the plantar forces I am talking at the joints. Using the analogy above.

    If the tibia does not externally rotate Mr Aussie how else would the orthoses resolve the knee pain (pat-fem syndrome).
    Last edited: Jun 30, 2006
  11. markjohconley

    markjohconley Well-Known Member

    hey mr biomech whatever you're on save it for the weekend........ you're unlikely to get a response when you address these "gentlemen" so......
  12. biomech

    biomech Member


    What does that mean ?

    Are you implying I am on illegal substances?

    Simple question.
  13. Craig,
    When you say no correlation in bold letters do you mean that the linear model did not fit well? r square? Did you attempt to fit curvi-linear; cubic quadratic etc.? Did you attempt any scale adjustment- log etc.? As you know, saying "no correlation", may well be misleading to some readers.
  14. Biomech,
    Nice attitude. Obviously went to the Spooner school of charm and grace. Cool Cool. But not the way to get what you want.
  15. Craig Payne

    Craig Payne Moderator

    Pearson's r was used.
  16. Craig Payne

    Craig Payne Moderator

    It means when you post messages like:
    ...you will motivate people not to help and get replies like:
    and you expect a response from me when I do not know you and you say this:
    .... anyone that knows me knows I am not Australian.

    But I will respond anyway - where did I say "If the tibia does not externally rotate "? I said: "Where did you get that from? - it never been true"in response to your comment of "for every degree of pronation at the STJt there is an equal amount of internel rotation of the tibia" . I can only assume you are not familiar with all the research on coupling, that shows its not one to one and varies between pronation and supination. I assume you are also unfamilar with all the work on foot pronation/tibial rotation NOT being associated with knee pain (discussed here).
  17. OK. So saying no correlation is probably not the right expression. Agreed? Sorry Craig, just feeding the devil inside. Have a good weekend :)
  18. Quite right too, descended from convicts don't you know. ;) Only joking on a Friday night.
  19. Craig Payne

    Craig Payne Moderator

    bugger off .... its 4.00AM Saturday and I on way to airport to talk all day in sydney.
  20. That, my friend, is what you get for living on the other side of the world- no Friday night. ;)
  21. I really have a difficult time convincing myself to spend any time to answer questions from individuals who don't have the courtesy to give me their real name in public forums. I'm sure I am not alone in my feelings on this. If you want a reply, then tell us who you are and ask respectfully, or you won't get what you want, at least from me.
  22. Craig:

    I think we probably agree, but I had to step in and clarify your "black and white statement" since foot orthoses do work and are commonly used in improving athletic performance and preventing injury in uninjured individuals. I'm sure you just rushed in writing your statement, getting ready for your talk in Sydney. Craig, do the Harbour Bridge Walk for me since I had a great time doing that the time I lectured there in 2002.

    The term "masking of symptoms" is erroneous, misleading and is another one of Ed Glaser's terms I don't like. Orthoses don't mask symptoms, they cure injury. Does treating an infection with antibiotics "mask symptoms"? Does doing an ORIF on an ankle fracture "mask symptoms"? Does decreasing the tensile stress in the posterior tibial tendon during weightbearing activities so that the tendon heals and becomes nonpainful with a foot orthosis "mask symptoms"? No, no and no. A local anesthetic will mask symptoms since it prevents the central nervous system from being aware of a noxious stimulus. Ice application will mask symptoms since it numbs and temporarily reduces inflammation to an injured area. However, foot orthoses do not numb or block neural pathways to injured areas which would be the best clinical example of "masking symptoms". Foot orthoses mechanically reduce the pathological forces and stresses that allow injuries to heal so that the pain is reduced.

    Orthoses do alter externally applied forces and pressures, alter internal forces, internal moments and inernal stresses, and alter motion patterns of the feet and lower extremities. We have the research evidence to support these mechanical effects that foot orthoses have on the human locomotor apparatus. Is this "biomechanical correction"? I don't really like the term "biomechanical correction" either, since this implies a permanent change in biomechanical function from foot orthoses. I think that a much better term for what foot orthoses do is biomechanical optimization.

    Biomechanical optimization: An improvement of the kinetics and kinematics of the locomotor apparatus of an individual so that weightbearing function is enhanced and the likelihood of musculoskeletal injury is minimized.
    Last edited: Jun 30, 2006
  23. Orthoses certainly have the capacity to alter kinematics and/ or kinetics, and, may even improve function, but optimization suggests making the best or most effective use of something. Can we say with certainty that this is what orthoses do?
  24. Good point, Simon. Certainly our goal with foot orthoses is "biomechanical optimization" but we probably never achieve it with foot orthoses alone. However, "optimization" does describe a process where both the positives and negatives of a process are taken into account to achieve a goal, whereas "correction" describes more of a removal of defects in a system to make it function better. I am open to suggestions for a better term.

    1. vt enhance the effectiveness of: to make something function at its best or most effective, or to use something to its best advantage

    1. alteration that improves: an alteration that removes an error

    Microsoft® Encarta® Reference Library 2005. © 1993-2004 Microsoft Corporation. All rights reserved.
  25. Jonatan García

    Jonatan García Active Member

    4ª dimension

    Dear All,

    I have been reading the latter discussion, and agree with that the foot orthoses operate reducing "stress in injured tissues", reducing the magnitude of pathological forces and/or stresses acting on selected structural components of the foot and lower extremity, …
    I have been charmed with the concept of biomechanical optimization.

    I think also that the foot orthoses work for the alteration that provokes in 4 ª dimension at which the foot is employed, the time. I think that the biomechanical optimization also happens to temporary level, since it would not be the same thing, to support a pronation of 5º during a second in the settled phase of the march, that during 5 seconds.

    Even I have thought of doing a review on the topic, to do a brief publication.

    Would that thinks about this concept, be in the certain thing?

  26. R.S.Steinberg

    R.S.Steinberg Member

    Dear All,

    Why is it that too many of you hang your profession only on published studies, any studies.

    Why is it that too many of you disregard the years of real life, real practice expereince?

    Comments on two Subjects:


    Some please explain to me why in my 28 years of practice experience, I find that my patients who failed pre-fabs and other initial conservative care, do remarkedly well with prescription functional orthoses - made from plaster casts. Further, explain to me why so many of them call to have 2nd and 3rd pairs for other shoes/activities? Oh, and in case you aren't following this runaway train wreck for podiatry, even if their first pairs were paid for by insurance, the 2nd and 3rd pairs are paid for outof the patient's own pocket. And, why is it that my more serious athletes, yearly, come in religiously for new prescription functional (not just customed, but corrective) orthotics.?

    Why isn't my hands on practice experience more valuable then a study that could be biased.


    Why do some of you continue to bring up the totally flawed study done by an unqualified radiologist? The last time I checked, radiologist don't touch patients and lack the training and experience to examine, diagnosis, or treat sports medicine conditions.

    Again, I want to throw in your face, real practice experience. When the Dornier EPOS Ultra is used in the method approved by the US FDA, and applied to the patients that meet the criteria that accepted and approved by the US FDA, remarkable results are seen? Why are my patients - going back nearly 7 years - recommending ESWT to their family members and friends, and come back to have the symptomatic other foot treated, begging me not to make them go through the 6 months of hell that the US FDA requires?

    Why? Why? Why?

    Dr. Payne,

    I see you are coming to Chicago in December. I want to promise you two things, a taste of a Chicago Winter, and a taste of a Chicago dinner on me. Are you up for it ??
  27. Craig Payne

    Craig Payne Moderator

    Unfortunatly I have had to pull out of the mtg :( ... twins on the way and due then :) ... me in big trouble if go :(
  28. Craig:

    Glad to see that the twins are now public news. Give my regards to Mimi and wishing you the two the best with the new additions to your family.

    By the way, I'm "expecting" my first grandchild in the next few weeks and I'm feeling very old as a result. My wife and kids now tell me that I need to soon decide if I will be called Grandpa, Papa, Grandad or some other "old" name. I have been told that the best thing about being a grandparent is if you get tired of the grandkids, you can always send them back home to the parents. :rolleyes:
  29. biomech

    biomech Member

    no nearer

    I see the question still has not been answered.

    How and what does the orthoses do to elleviate the pain in the knee

    How and what does the orthoses do to elleviate the pain in the lower back.

    How did it level the hips and resolve a functional scoliosis?

    Simon was a tutor down south at Plymouth University I think. I can just see him now asking this question to his students.
    Statement earlier..."that the foot orthoses operate by reducing "stress in injured tissues", reducing the magnitude of pathological forces and/or stresses acting on selected structural components of the foot and lower extremity, …"
    but how does it do this. What is happening to the skeleton itself, what is rotating, shifting etc to explain the reduction in the above.

    Anyone can make the statement above but HOW does it do this.
  30. Biomech, as far as I know, I don't know you and you don't know me, so until such time that you reveal you identiity, I would prefer it if you didn't make sweeping statements as to what I may or may not have asked as questions to students when I was a Lecturer and/ or Head of School of Podiatry at the University of Plymouth.

    You clearly have a far greater understanding of biomechanics than myself or any of the other people who have responded to your initial request, which was: "I need articles on what the orthoses does and what effect it has on posture". Since after I gave you direction to a list of references which may have helped you resolve the question, you then decided that this was not what you wanted and really what you want to know is: how a pair of orthoses which you give little, if any, detail on had a beneficial effect in a patient whom none here, but yourself has seen and to which you have offered little if any detail regarding. So enlighten us, what mechanical effect did these orthoses have and how did you measure this?

  31. Craig Payne

    Craig Payne Moderator

    I would somewhat disagree, it does not matter if the kinematics (~motion) are altered, it the altering of the kinetics (~forces) that changes the forces going through the tissues (ie the injured structures). Altering kinematics (~motion) on its own does not necessarily change the kinetics (~forces) and you can change kinetics (~forces) without necessarily altering kinematics (~motion).
  32. Simon, Craig, and Colleagues:

    Even though I would tend to agree with Simon more on this one, Craig does make some good points. However, I don't think that either Simon or Craig have adequately explained the function of orthoses with enough detail to satisfy me given our current knowledge of foot orthosis function.

    Foot orthoses may alter both the kinematics and/or kinetics of the foot and lower extremity. Kinematics may not be altered if kinetics are not also altered since any change in motion of a body segment must also be accompanied by changes in accelerations of segments which are, in turn, dependent on a change in forces and/or moments on those segments (i.e. a change in kinetics).

    If the goal of foot orthoses is to alter the external forces acting on the body and/or the internal forces acting within the body to reduce the tissue stresses that are causing an injury, then a change in kinetics is required but a change in kinematics is not necessarily required. However, if the goal of foot orthoses is to change the gait pattern of an individual (e.g making a child with outtoe gait walk in a more rectus position), then a change in kinematics is required that may or may not necessarily rely on the orthosis "pushing the foot into the proper position" by a direct change in kinetics of the foot and lower extremity.

    More specifically, many gait changes (i.e. changes in kinematics) seen both in patients with and without neuromuscular disease may rely on how the central nervous system (CNS) alters the magnitude and temporal firing pattern to the lower extremity muscles in response to foot orthosis intervention (Mundermann, A., B.M. Nigg, R.N. Humble and D.J. Stefanyshyn: Orthotic comfort is related to kinematics, kinetics, and EMG in recreational runners. Med Sci Sports Exercise, 35:1710-1719, 2003; Mundermann A, Wakeling JM, Nigg BM, Humble RN, Stefanyshyn DJ: Foot orthoses affect frequency components of muscle activity in the lower extremity. Gait and Posture, 23:295-302, 2006).

    As such, both the kinetics and kinematics may be changed not so much by the foot orthosis pushing on the foot and the foot going in the direction of the push from the orthosis. Rather, the kinetics and kinematics of the foot and lower extremity may be changed by the foot orthosis altering the magnitudes, plantar locations and temporal patterns of ground reaction forces acting on the plantar foot during weightbearing activities so that the CNS responds by then altering the temporal patterns and magnitudes of contractile activity of the lower extremity muscles to improve the metabolic efficiency of gait, decrease the pain of gait or to prevent injury to the individual from occurring.

    Leaving out a discussion of the huge effects that the CNS has on how gait changes are or are not produced with foot orthosis intervention will result in only a small part of the story being told about how foot orthoses may function to treat a wide variety of abnormal gait patterns and musculoskeletal injury in the bipedal human.
  33. biomech

    biomech Member

    Define the kinematics and kinetics of a rearfoot varus causing excessive pronation when an orthoses is prescribed ?

    What effects does the orthoses have on the kinematics and kinetics of the leg as a whole.

    Again, what do orthoses do ??
  34. This doesn't make sense???

    In order to answer this you need to be more specific. For example, there is reasonable data which suggests that CoP will shift medially with a varus post and laterally with a valgus post. Just saying orthoses doesn't really help. Like I said, go read the references.

    The following single aspect of the multi-aspect problem may help you understand the complexity: Imagine an orthoses, which we cut across in a bacon slicer from medial to lateral so that we are left with very thin slices. If each of these slices from proximal to distal represents a sequential instant in time during contact phase, and the CoP is positioned somewhere at the supporting interface of each slice during that slices instant in time. Let the CoP be the orthotic reaction force ORF. The vertical and horizontal components of the ORF is then dependent upon the incline of the slice at The ORF point of action. In other words, the force is angled to the plane of the orthotic slice. The moment produced about a given joint is dependent upon the perpendicular distance of this force vector to the instantaneous axis, which is also moving in time and space.

    So this is only really the start of the problem, because we also have to figure in internal moments.

    Dave Smith, this is probably over to you.
  35. Craig, I agree in general with your statement above, however, research demonstrates that foot orthoses alter kinematics and or kinetics, which was the question I was answering.

    Been thinking about this today:

    Without kinematic change in response to orthoses is sagittal plane facilitation theory fundamentally flawed?
  36. Also co-efficient of friction between orthoses and hosiery and hosiery and skin will be important... And probably the phase of the moon, the strength of the pound against the dollar, whether or not you believe in orthoses etc etc.

    My heads hurts just thinking about this again, Kevin and Dave will recall I started trying to analyse this problem some months ago and stopped because it made me insane (AGAIN). :confused: Mommy please let the bad men go away. It was pig I'm sure it was.

    P.S. Kevin I've taken up running, so maybe soon I really will be seeing pigs.
  37. efuller

    efuller MVP

    On reviewing this thread, I can see that part of the problem is people are living in different paradigms. In the tissue stress paradigm, you cannot forget the redistribution of forces. That is how orthoses work. So, Biomech, when you ask, what you think is a simple question, you got an answer that does not make sense to you. The Mr. Aussie part of your question did not help the tone either. Because of your lack of knowledge of the literature, you felt you were being blown off. Well, I'll try and give you a brief synopsis of the tissue stress approach.

    Things hurt because they have too much stress placed on them. Things do not hurt because there is a rearfoot varus. There may be a rearfoot varus and when the foot is placed on the ground the lateral forefoot hits and force in this location creates a ponation moment at the STJ and the STJ will pronate until somehting stops it. The lateral process of thetalus hitting the floor of sinus tarsi is one thing that will stop the STJ from pronating further. Thus a rearfoot varus may cause sinus tarsi pain because there is high force at the lateral process of the talus. A pronation moment is created when the Center of pressure (COP), which is the average point of force is lateral to the STJ axis. If the STJ is not pronating then there must be a supination moment from some other source countering the pronation moment from the ground. (When the net moment is equal to zero there will be no angular acceleration.) A treatment that shifts the location of the center of pressure more medially will decrease the pronation moment from the ground and hence decrease the force needed in the floor of the sinus tarsi to resist the pronation moment from the ground, thus reducing pain.

    That is how orthoses work. You cannot "forget" the redistribution of forces. Biomch, if you feel that this explanation is useless then I cannot help you in your quest to understand how orthoses work. This analysis can be expanded, and has been expanded to other structures (e.g. the leg) in the literature sited.

  38. To see pigs, you will need to run much, much faster..... ;)

    BTW, I became a grandpa today.....7 lbs, 9 oz....a boy. Someone to share life with in my older years and to carry on the Kirby name into future generations......what a wonderful and amazing thing this life is!!
  39. biomech

    biomech Member


    Thank you efuller that was more like the answer I was expecting.

    BTW you stated the literature cited, where is this.

    I am not a podiatrist, i was prescribed these and was wondering how they worked as there is not much to them and they cost me a fortune.

    I would like the links though to the cited literature as I am intrigued

    Boris Karloff
  40. deco

    deco Active Member

    "I am not a podiatrist, i was prescribed these and was wondering how they worked as there is not much to them and they cost me a fortune"

    I have been following this thread for a while now and your last post has outlined exactly where you are coming from. I dont think this is the correct forum for your question, perhaps you could contact the podiatrist who origionaly prescribed these for you? Whoever prescribed them for you would be the most appropriate person to outline how they work for you.

    Best Wishes

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