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Foot orthoses and the placebo effect

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Craig Payne, Aug 11, 2005.

  1. Craig Payne

    Craig Payne Moderator


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    I am in one of those moods today ... :rolleyes:

    We all know about the possible placebo effect of our treatments etc etc, but tend not to pay a great deal of attention to it...

    We have a plantar fasciitis RCT in press at the moment - subjects randomised to one of 3 "inserts" (all of which can be purchased from a retail pharmacy) - these are devices that I would never consider using clinically (they are that bad) ..... to our dismay all but 3 of the subjects got better :confused: - the world did not end then....

    Now just finished the number crunching on a second plantar fasciitis RCT. One group got the comfort model of Formthotics (not the regular one most use) and the other group got the same, but they were modified depending on the presence of risk factors for plantar fasciitis according to a strict protocol (ie tight calf muscles (lunge <38 degrees)--> heel raise; high force to establish windlass --> lateral column elevation; etc) --- we would have thought that this time we would find some differences .... but no - there was no difference between the two groups and everyone showed some symptomatic improvement :( ..... now you can see why I am in a "mood".

    At the end of the day, I just now think that when it comes to clinical trials with foot orthoses, that the placebo effect and Hawthorne effects are so powerful, everyone seems to get better .... this is forcing me to have a major rethink about how we really should be designing our foot orthoses clinical trials.

    On a positive note we do have results from a hopelessly underpowered n=8 RCT in which 4 were modifed to the above protocol (all got better) and 4 were modified to do something unethical (ie make them worse) (and they did not get better).

    What say you?
    Last edited: Aug 11, 2005
  2. javier

    javier Senior Member

    Hello Craig,

    I do not think that we can talk about placebo effect due to foot orthotics. I have been wondering about the same subject in my clinical practice. All of us have visited patients wearing different types of custom-made and OTC foot orthosis and many of them report an improvement on their conditions although from your own opinion their orthotics are useless.

    This situation have been keeping me puzzled since I knew Kevin Kirby theories and his mechanical approach to foot function (thanks Kevin :) ) . It is clear that anykind of foot orthotics will produce a mechanical response on the foot, although this effect it is difficult to measure. A device placed inside the shoes will produce a change on GRF and on foot loading force that have its effect on foot anatomical structure and components.

    You can try using a simple insole adding a wedge for conditions such as peroneus tendonitis and you will be amazed how the patient reports and improvement. Of course, it depends on you place the wedge.

    Why low profile orthoses do accomplish a therapeutic goal? You have two answers:

    1. Because they influence on foot mechanical moments.
    2. Luck (I know it is not a logical explanation, but How can you explain that a low profile design can influence on foot mechanical moments at the right place?)

    Forget mood, your research help clinicians like me to take off "luck" from the equation and take decisions based on science.
  3. Craig Payne

    Craig Payne Moderator

    Thats the puzzling thing about foot orthoses:
    ...given that what we are dealing with (ie plantar fasciitis), how can foot orthoses have a mechanical effect via placebo :confused: ??? ..... and I used to know what I was doing :eek:
  4. javier

    javier Senior Member

    They can not. Any foot insert with certain a shape and physical properties due to its materials have an influence on moments during foot loading.

    Also, you have to consider the body response to changes on GRF through propioceptive system.

    I am curious to know if these low profile devices are able to maintain their achievement during long term periods or their effectiveness is limited on time.

    Finally, I wonder about reliability from patients symptomatic improvement perception. Although, this is the most used control tool by us.
  5. javier

    javier Senior Member

    I would like to add that if you want to consider the placebo way, the symptomatic improvement perception could be related to endorphins release by the brain.

    Although, this possibility is quite twisted, if it would be true we could make lots of money among foot feetishists due to foot orthotics brain exciting properties :) !!
  6. Javier's reply is very logical. All in-shoe "supports" (i.e. those that have an arch shape) will alter the magnitude, location and temporal patterns of reaction force acting on the plantar foot. I will call this force plantar reaction force (PRF) to distinguish it from the reaction force exerted by the ground, ground reaction force.

    If we can then assume that any "arch supporting insole" that increases the PRF at the level of the midtarsal/midfoot joints will also increase the magnitude of rearfoot dorsiflexion moment and increase the magnitude of forefoot plantarflexion moment, then it is quite apparent that all of these arch supporting insoles also have the potential to mechanically affect the internal forces applied to the tension bearing elements of the plantar arch of the foot (i.e. plantar fascia, plantar ligaments, plantar intrinsic, deep flexor and peroneus longus muscles).

    In other words, since the plantar fascia is a tension-bearing element of the plantar arch of the foot that, when under tension, causes a rearfoot dorsiflexion moment and a forefoot plantarflexion moment (Kirby, Kevin A.: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002, pp. 117-118, 145-152), then any externally applied force on the plantar foot that also causes an increase in rearfoot dorsiflexion moment and a forefoot plantarflexion moment will tend to reduce the magnitude of tensile force on the plantar fascia. In turn, this reduction in tensile force on the plantar fascia will likely result in a reduction of symptoms associated with plantar fasciitis.

    Modelling the foot in this way allows one to see that any "arch supporting" addition to a shoe, no matter how oddly it is shaped, since it will increase the magnigude of PRF at the midtarsal/midfoot level of the foot, also has the potential to reduce the symptoms of plantar fasciitis. Even toilet paper placed in the arch of a shoe insole will lessen the pain of plantar fasciitis in some patients so that I tend to doubt that the placebo effect is the best explanation for the positive therapeutic results seen with various arch support designs for this common clinical pathology.
    Last edited by a moderator: Aug 12, 2005
  7. Foot fan

    Foot fan Active Member

    when it comes to pain - how can you be sure what is placebo and what is not? Pain is the brain's interpretation of something 'wrong' in the periphery, whether it is the brain telling itself the problem is 'fixed' or the problem being fixed seems irrelevant as the end result is the same - the pain is gone.

    Second to this, is the problem with the design of the studies or our mentality toward orthotic therapy - how can we be sure the results we see clinically with orthotics are really having an impact on the structures we think they are or if it is all a placebo effect. After all, our current evidence for orthotic therapy is anecdotal.
  8. Craig Payne

    Craig Payne Moderator

    No its not - there is evidence for it....its just the evidence to guide decision making between different types of orthoses that is lacking (...and the Hawthorne effect is hampering those efforts)

    Esp...keep an eye on what is coming up in a future issue of JAMA (Journal of the American Medical Association)
  9. Foot fan:

    Read any research lately?? Foot orthosis evidence, like Craig stated, has been in the literature for some time now. It is not just anecdotal. I suggest that you start reading the scientific journals so that you can keep more current of the research evidence regarding foot orthoses. Here are a few of the better ones that will improve your knowledge of the more current foot orthosis research:

    Kogler, G.F., Solominidis, S.E. and J.P. Paul: Biomechanics of longitudinal arch support mechanisms in foot orthoses and their effect on plantar aponeurosis strain. Clin. Biomech. 11 (5): 243-252, 1996.

    Landorf, KB and A.M. Keenan: Efficacy of foot orthoses: what does the literature tell us? Australasian Journal of Podiatric Medicine, 32 (3):105-113, 1998.

    Mündermann, A, Nigg BM, Humble, RN, Stefanyshyn, DJ: Foot orthotics affect lower extremity kinematics and kinetics during running. Clin Biomechanics, 18(3):254-262, 2003.

    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.

    Powell M, Seid M, Szer IA: Efficacy of custom foot orthotics in improving pain and functional status in children with juvenile idiopathic arthritis: A randomized trial. J. Rheumatology, 32:943-950, 2005.

    Redmond, A., Lumb, P.S.B., Landorf, K.: Effect of cast and noncast foot orthoses on plantar pressure and force during normal gait. JAPMA, 90 (9): 441-449, 2000.

    Williams, D.S., McClay-Davis, I., Baitch, S.P.: Effect of inverted orthoses on lower extremity mechanics in runners. Med. Sci. Sports Exerc. 35:2060-2068, 2003.
  10. jane dunbar

    jane dunbar Welcome New Poster

    orthotics and placebo

    I wonder if, because orthotics fill the shoe therefore reducing movement of joints etc the effect is deemed therapeutic by the wearer. :) :)
  11. Colleagues:

    Here's another article, soon to be published, demonstrating the mechanical effects of foot orthoses (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, Accepted for Publication, 2005).

    We are currently experiencing the beginning of the golden age of foot orthosis research. No longer will foot orthoses be considered in the same light as they were 20 years ago when I first began my practice. After reading these research papers on the mechanical effects of foot orthoses, I now hope that no one else still believes that "our current evidence for orthotic therapy is anecdotal".
  12. efuller

    efuller MVP

    Changes in muscle function could explain why no matter what you put in the shoe the patient gets better. (Orthoses in the wrong shoe). Perhaps the device in the shoe is a reminder to the patient that they need to walk differently.

    Eric Fuller
  13. casanach

    casanach Welcome New Poster

    Reverse placebo?


    I am wondering if a little knowledge is a dangerous thing. I do have a smattering of biomechanics experience i.e. 20+ years, and was therefore concerned when, a week before a walking holiday I lost my prescription orthoses. Being desperate I bought a pair of off the peg devices from Boots which despite proudly stating " 4 degrees of varus control" did absolutely nothing for my rearfoot varus "tibia varum". I repeat absolutely nothing. I stood on them and then off them several times, walked for miles and frankly had to look to make sure I was wearing them :( They ended up in the trash can because I couldn't justify the weight of carrying them for the rest of the holiday.

    With regard to the placebo effect, does this mean that I have no faith in my own knowledge and need counseling or..........

    Seriously if I can see that these flexible devices are virtually useless how is it that so many patients are so easily pleased?

    Best wishes,


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