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Direct Mechanical vs. Neuromotor Effects of Foot Orthoses

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Kevin Kirby, Jan 2, 2009.

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    We have been having some very important discussions recently on the different possible functions of foot orthoses. First, foot orthoses may exert a direct mechanical effect that may be predicted by changes in ground reaction force (GRF) from the orthosis on the plantar foot relative to the joint axes of the foot and lower extremity. Second, foot orthoses may, by altering the location, magnitude and temporal patterns of GRF on the foot, cause a change in afferent input into the central nervous system (CNS) that will then cause a change in efferent output to the lower extremity muscles that will, in turn, alter the muscle activity of the foot and lower extremity during weightbearing activities.

    Here is the segment from my latest posting to Charlie Baycroft, which details some of my thoughts on this vital subject.

    This is an excellent topic to start as we move into 2009. Happy New Year!!
  2. Craig Payne

    Craig Payne Moderator

    I have made my views known in the thread on Sensory effects of foot orthoses and on the proprioceptive crap in the thread on The Other Proprioceptive Medicine

    I have no doubts about the importance of plantar sensory perception (see: Cutaneous reflexes contribute to stability during walking ) ... I simply remain unconvinced about the role of and relative importance of neuromotor or neurophysiological pathways for foot orthoses to exert their effects (I would love to be convinced about them though).

    Having a theoretical pathway/model is NOT evidence that it exists.

    I also struggle to see how a neuromotor response is even a good thing - to respond to a foot orthoses this way requires additional muscular effort, which from an efficiency point of view has to be a bad thing.

    As an aside, I did recently review a patient with a colleague who was totally convinced about the neuromotor pathway based on this one patient. The apparent kinematic response that the patient had to a relatively benign prefabricated foot orthoses did appear substantial. HOWEVER, on closer look, they had very low supination resistance which would easily explain the magnitude of the apparent large kinematic response ... no need to 'grasp' for sensory explanations.

  3. Craig and Colleagues:

    If orthoses always pushed the foot into a new position, without influence from the central nervous system (CNS), then there would be a lot more inversion ankle sprains from foot orthoses. The research that has led to the Preferred Motion Pathway model by Benno Nigg and colleagues certainly seems to indicate that there is considerable influence from foot orthoses on the EMG response of lower extremity muscles.

    Here is an experiment I have been doing for the last 20 years that, I believe, confirms the neuromotor influence of the CNS on the mechanical effects from foot orthoses. Take an individual and have them walk barefoot at a preferred speed and measure the distance covered in 10 steps and note whether subtalar joint supinates or pronates in late midstance and propulsion. Also note the length of the propulsive phase. Now, take a piece of 1/4" (6 mm) adhesive felt and adhere it to the plantar first metatarsal head of the individual while barefoot and note whether the increase in external subtalar joint (STJ) supination moment from the sub-1st metatarsal head indeed causes an increase in STJ supination motion, especially in late midstance and propulsion. Also note the stride length, which normally decreases with the sub 1st pad in place. The experiment can also be done with adhesive felt pads in the medial arch, medial heel and 1st metatarsal head to further increase the STJ supination moment to see how the STJ responds in late midstance.

    If only the direct mechanical effects of the orthosis influenced the foot, without any influence from the CNS causing altered muscle firing activity in response to the mechanical effects of the orthosis, then increased varus wedging in the forefoot and/or rearfoot would keep the foot supinated throughout the stance phase of gait, without increased late midstance pronation. However, this is often not the case. The ability of the CNS to influence the magnitudes and temporal patterns of muscle activity in the foot and lower extremity in response to alterations in ground reaction force patterns, which is consistent with the Preferred Motion Pathway model, is the most reasonable explanation for the variable effect of different degrees of varus wedging with foot orthoses.
    Last edited: Jan 4, 2009
  4. pod29

    pod29 Active Member


    Why does a neuromotor response to a foot orthosis have to mean more muscle work? Why couldn't a decrease in subtalar joint pronation moments(via use of CFO) lead to a decrease in muscle activity in muscles that apply a supination moment to the Sub talar joint?


  5. Craig Payne

    Craig Payne Moderator

    How else would a neuromotor or sensory (or dare I say, proprioceptive) response work? If there are excessive STJ pronatory moments and if there is to be a neurmotor or a sensory response to a foot orthoses then where will the STJ supinatory moments come from? ... they can only come by increased activity of the post tib muscles or by increased activity of the external hip rotators --- surely that has to be a bad thing (esp if the patient has a post tib problem?)
    That decrease in muscle activity would be in response to a kinetic (ie mechanical) effect of the foot orthoses.

    I really have an open mind on this one..... but I still just don't get it.
  6. pod29

    pod29 Active Member

    The decrease in muscle activity still has to be via a neuromotor pathway, does it not? Yes it is a kinetic change at the joint from the foot orthoses, however it is possible that this kinetic change will cause muscle activation changes via mechanoreceptors in the joint capsule and surrounding ligaments. Is this not a sensory or neuromotor response?


  7. Craig Payne

    Craig Payne Moderator

    I think we talking at cross purposes. What I am arguing against is the claims that for orthotics to work by changing the plantar sensory input signal can only do so via increased muscle activity (perhaps we call this a primary response). What you are suggesting, is that there is a kinematic and/or kinetic (mechanical) response that results in the neuromotor changes (perhaps we call this a secondary response).
  8. pod29

    pod29 Active Member


    Okay Craig, point taken. I feel it is critical to discriminate this difference when discussing the sensory or neuromotor effects of foot orthoses. The effect of foot orthoses on sensory cutaneous afferents may be quite different to the effect on joint mechanoreceptors. However, they are both "sensory" or "neuromotor" responses.

    The "secondar neuromotor response"(C payne 2009) is quite interesting and may go a way to help explain the effect of foot orthoses in the treatment of more proximal conditions. I think we will hear a lot more about this in the near future. Watch this space!

    P.S - Sunday is Monday in Qatar, whats your excuse for working on a Sunday?;)


  9. Charlie Baycroft

    Charlie Baycroft Active Member

    Craig and Kevin
    I am quite enjoying the exchange of ideas between the two of you about this issue.
    There is a great deal of good research on the mechanical effects of foot orthoses on cadaver specimens, thanks to Kevin and others with the tenacity to prepare these specimens and do this somewhat unappealing (to me anyway) type of work.
    This has led to a tendency to assume that a living foot and leg should behave the same way. However, this does not appear to necessarily be the case but it has definitely greatly influenced our thinking about foot orthoses.
    More recently, there have been studies that revealed canges in EMG activity and postural stability in association with the wearing of mechanical foot orthoses.

    Effect of foot orthoses on lower limb muscle activation: a critical review
    AnnaLucy Hatton^1*, John Dixon^1, Keith Rome2 and Denis Martin1
    ^1Centre for Rehabilitation Sciences, University of Teesside, Middlesbrough, TS1 3BA, UK 2AUT University, School of Podiatry, Division of Rehabilitation and Occupational Studies, Auckland, New Zealand
    Foot orthoses can be a valuable component of musculoskeletal rehabilitation, improving lower limb alignment, controlling motion and providing shock absorbency. Recent evidence suggests foot orthoses may also have a significant effect on lower limb muscle activation in young, healthy adults. This review examines the evidence for changes in muscle activation patterns when wearing orthoses, and explores the proposed mechanisms by which foot orthoses may bring about changes in lower limb muscle activity. Based on the current results it is proposed that different mechanisms may occur by which orthoses affect muscle activity, due to their differing construction and design.

    This review of the literature relating to the effects of foot orthoses on muscle activity was recently published in Physical Therapy Reviews 13:2, 2008. I will try to summarize this over the next few days or can forward a copy of the paper to those who re interested.

    The Neuromotor effects of foot orthoses are certainly not well appreciated or understood. I would tend to agree with Craig that these effects are probably not mediated by superficial neuroreceptors (pain, light touch and vibration sense) although it is interesting to observe the change in posture of the foot when stimulating the plantar surface in performing the Babinski reflex test. The recent discussion of taping is perhaps also relevent. Various authors have indicated that tape soon stretches and looses much of it's mechanical effect yet, it can remain effective in altering foot function and relieving symptoms for several days.

    Can we understand lower extremity function properly from a purely mechanical basis? I don't think that we can. The nervous system is far to intricate, elegant, sensitive and effective to ignore.

    In the deeper layers of the dermis there are:
    Pacinian Corpuscles, which respond to deep pressure,
    Ruffini end organs that respond to skin stretching and
    Merkel's Corpuscles that respond to tissue deformation.
    I think that these types of nerve endings are also present in joint capsules.
    In muscles there are muscle spindles that monitor the tension withing the muscle and Golgi apparati in the muscle tendon junctions that have a similar role.
    All of these mechanoreceptors are constantly monitoring mechanical forces (extrinsic and intrinsic) throughout the musculoskeletal system.
    Afferent stimuli from these mechanoreceptors flow along sensory nerves and are processed in the dorsal horns of the spinal cord, at the spinal segments where they are involved in relex activity like the knee jerk reflex and also at higher levels in the CNS.
    Efferent stimuli then travel via the motor nerves to alter the activity of muscles either in whole or in part because muscles are actually made up of many groups of fibres that can fire in various combinations. Efferent stimuli can also cause muscles to relax or can pre-set (or tune as Benno Nigg describes) muscles to prepare for an anticipated event. I find all of this terribly complicated but intriguing.
    I have said before that the human body does not always respond as mechanics would predict. If I push you, the mechanical force that I apply will not necessarily make you fall over. You can remain standing partly because of Newton's ? 2nd Law of action reaction but primarily because neromotor activity responds to this pertubation by stabilizing your body.

    Pain can be caused by a sustained posture that overstimultes mechanoreceptors and activates Wide dynamic range cells in Lamina 5 of the dorsal horn of the spinal cors to transmit the stimuli recieved from them to centres in the brain that percieves them as pain. Thus pain can be felt where there is no tissue damage, inflammation or presence of pain peptides. Such pain can be rapidly resolved by any modality that reduces the tension in the tissues that is overstimulating the mechanoreceptors.

    The argument of biomechanical and neuromotor effects of foot orthoses may be appraoched from an either/or or both/and perspective. I actually prefer the latter. There is certainly no doubt that FO's produce mechanical (kinematic and kinetic effects) there is also no doubt that by changing the surface under the foot we are altering the tension in various tissues (throughout the body) and stimulating changes in neuromotor activity.

    IMHO. I think we can only fully appreciate the effects of foot orthoses on the function of the lower extremity and the body as whole by learning more about and appreciating properly the neuromotor effects as well as the mechanical ones.

    Appreciating the neuromotor effects opens up the possibility of prescribing the devices in such a way as to hve a desirable effect on muscle activity or postural stability and this is an aspect of orthotic therapy that I have not seen much interest in to date.
  10. I believe that definitions need to be clarified here so that we better understand each other. Let me propose a few:

    Direct mechanical effect of foot orthoses: The kinetic and kinematic effect on the foot and lower extremity that is caused by the change in the location, magnitude and temporal patterns of ground reaction forces that results from direct mechanical contact of the foot orthosis with the plantar foot.

    Neuromotor effect of foot orthoses: The kinetic and kinematic effect on the foot and lower extremity that is caused by changes in sensory input to the central nervous system from the mechanical effects of the foot orthosis on the plantar foot that results in changes in the magnitudes and temporal patterns of motor stimuli from the central nervous system to the muscles of the foot and lower extremity. The afferent inputs into the central nervous system that may lead to the changes may come from sensory organs within the skin, joints, muscles, tendons, eyes, inner ears or other areas of the body.

    Hope these definitions will allow us to have a more meaningful discussion on this important topic.
    Last edited: Jan 4, 2009
  11. I totally agree with you on this one, Charlie. Good quote!
  12. Charlie Baycroft

    Charlie Baycroft Active Member

    Kevin. I was thinking today of suggesting that we need to define what we mean by Direct mechanical effect and Neuromotor effect but, as usual, you are too quick.

    Having these definitions is the most important aspect of better understanding the effects that foot orthoses can have on various parts of the body.

    To me, it is a bit like mastering a video game. Thanks to the excellent work of many people over the past 30+ years, there is a good appreciation of the direct mechanical effects that can can be produced and how they can potentially alter the function of segments of the lower extremity in accordance with the laws of physics. I would say that Podiatry, in general, has mastered level 1.

    Level 2 begins with the realization that segments of the living body do not always respond to mechanical forces in a way that can be predicted from the laws of Physics and this is because the living body can process sensory input and produce its own unique response. Mastering level two will not be easy because we do not have the clear and consistent physical rules of level 1 to guide us. We are faced with learning new rules and exploring avenues of investigtion and thought that may often end in dead ends.
    The existing observations of the various effects of FOs on EMG activity and postural stability are a beginning as are ideas such as those of Benno Nigg about muscle tuning (feed forward neuromotor function) and the preferred path theory that explains why you can sometimes recognize someone from a distance by the way they walk or run.

    Some Podiatrists may be upset to realise that "just when we thought we really understood how orthotics work, we are confronted by new questions." Maybe some people will decide it is better to ignore/deny these new challenges and just keep playing level 1. This can be justified on the basis that in a clinical setting orthotics achieve a very high degree of patient satisfaction and the exact mechanism by which these good effects are achieved is of little practical significance to the therapist and patient once the problem has been solved.

    However, better understanding and eventually being able to utilize the potential of foot orthoses to improve the neuromotor function of the lower extremity may well enable the practitioner to provide even more beneficial effects on foot and leg function.

    Consider the recent but as yet unpublished study by Isuke Hiruma, which was presented in a poster at the Australian Sports Med Conference in Adelaide. He found that the customized devices used had significant effects on static and dynamic balance immediately and at 6 weeks follow-up. This is not so surprising because several other studies have also indicated that foot orthoses of various types can improve postural stability. However, he also documented that the improvements in static and dynamic balance at 6 weeks were also present when the subjects where not standing on the devices.
    So, here is a puzzle for those who are skeptical about orthotics having neuromotor effects. If the improvement in postural stability persists when the patient is NOT standing on the devices can it be explained in by the direct mechanical effects of the devices?

    I take Craig's point that he objects to people labelling devices as "proprioceptive" just because someone had better balance while standing on them. The improvement in balance that is observed when a person stands on the devices could certainly be explained (plausibly if not physiologically) in referrence to mechanical principles and we do not yet know enough about the neuromotor effects of orthotics to validate such claims.

    However, we will not gain this understanding by refusing to acknowledge the fact that there are observations about the effects of foot orthotics that strongly suggest that the have a great potential to alter the neuromotor function of the foot, leg and higher structures.

  13. Ian Drakard

    Ian Drakard Active Member

    Hi Craig

    First post so go easy

    I can see the point about efficiency, but if we are intervening then it is to solve a problem- if this is achieved by increasing muscle activity in terms of either level or timing, does it matter unless it causes a different problem?

  14. Charlie Baycroft

    Charlie Baycroft Active Member

    If tonic/postural muscles were not firing constantly gravity would cause us to collapse in a heap on the ground. If Phasic muscles did not fire we could not move from place to place.

    I was just reviewing the thread about "do foot orthotics weaken the Intrinsic muscles of the foot". The insistance on a purely direct mechanical effect of foot orthoses, without neuromotor effects is the basis for the belief that they do weaken the intrinsic and extrinsiv muscles of the foot. If the posture and movement of the lower extremity are "controlled" by the mechanical effects of the orthoses then the muscles would stop firing weaken and atrophy.

    The research presented in this previous discussion clearly supports the opinion that orthoses do not cause the muscles to stop firing, weaken or atrophy. Craig noted that there was a tendency (but not statistically significant) for the muscles to strengthen. If so, this would be a neuromotor effect.

    Please recall that the body is not a passive mechanical system. We are complex living and dynamic beings and our bodies have the ability to adapt to and respond to changes in our environment by neuromotor, hormonal, cellular and chemical mechanisms.

    Hans Selye described this well in his work on stress-adaptation.

    If one would apply the reasoning that orthotics should not increase the activity of muscles at some times during gait then he/she is also suggesting that athlete's should not train to improve their functional capacity.

    Go back to the foot/floor/inside of the shoe interface. Here we have a situation in which GRF and the weight of the shoe are requiring the foot to adapt to what is (from the perspctive of human evolution) a very unnatural environment. The foot tries to adapt to this environment there should be no surprise to note that this adaptation involves pronation. Adaptation to a hostile environment results in the creation of stress in various tissues and also in an impaiment of function.

    When we change the environment under the foot to one which is more compatible with the shape of the foot, the body will adapt to this as well. This adaptation is a neuromotor response.

    Physical therapists use techniques called neuromotor rehabilitation to improve the posture of various parts of the body. Vladimir Janda developed a method or postural retraining which involved actively supinating the foot to a more balanced neutral position, which he called the "short foot". He then had patients do exercises on unstable surfaces to induce pertubations to stimulate neuromotor adaptions to the new foot posture. Patients get better from this treatment and also "learn" to unconsciously adopt a new and more neutral foot posture. All of this is done without foot orthoses (so it takes a long time).

    I have frequently observed that patients who initially had a very pronated foot posture before using foot orthoses had a more neutral posture when standing in bare feet without the orthotics (after some months of using the devices). This is becaus the orthotics caused neuromotor adaptation of tonic/postural muscle function.

    Foot orthoses do have very significant neuromotor effects, which may be independent of their direct mechanical effects and may even be more significant in relation to their potential to improve the function of the lower extremity.

    Has anyone looked at the sequence of movements of the foot during swing phase? I have frequently observed that orthotics cause changes in these movements when the foot is off the ground. Is there a mechanical explaination for this or is it a neuromotor effect?

  15. This same phenomenon could also be due to shortening of the plantar ligaments in response to decreased tensile loads from the foot orthoses (creep phenomenon). I wouldn't be so certain that this is caused solely by a "neuromotor adaptation".
  16. Charlie Baycroft

    Charlie Baycroft Active Member

    Ligament shortening.
    I agree that there will wite likely be some adaptive shortening of overstressed ligaments when static and dynamic foot postures altered by the use of orthotics. Without orthotics ligament creep certainly does occur and makes the foot get longer and flatter as the person ages and tissues become less resilient. This process is accelerated in pregnancy due to the presence of realxin and every pregnant lady should have orthotics (if possible) to keep her dainty feet.
    Some of the cases that I referred to were children and the feet were still capable of a very significant amount of pronation but I do not have any measurements of navicular drift, drop or other data to dispute this on.
    On the other hand, ligaments have a very significant sensory function and when the tension increases in them messages are sent to the CNS to activate muscles to relieve the tension.
    No orthotics results in ligament creep and laxity.
    Orthotics allow ligaments to remodel as the persistant tension is reduced.
    Ligaments are no longer overtensioned and might shorten.
    In any event after using the orthotics the ligaments and other LE structures containing mechanoreceptor nerve endings get addapted to reduced tension. Patient stands without the orthotics.
    GRF promotes pronated posture BUT pronation past a certain point induces increased tension and stimulation of mechanoreceptors, which then fire and activate muscles to control the pronation.

    Result. Post orthotics the foot now has a less pronated static posture as a consequence adaptive and neuromotor consequences of having used the orthotics.

    Interesting that you can slice the same bread with the mechanical or neuromotor knife.

  17. CraigT

    CraigT Well-Known Member

    Very interesting discussion!
    I explain to patients that orthoses are somewhat like an office chair which has been adjusted to help your posture while sitting. While you are in the chair it is of great benefit, but it does nothing when you are sitting in other chairs. If you use this chair regularly, then you get the most benefit and, after a period of time, your body begins to 'learn' the better posture, and maintain it when you are in other chairs. This is why I also recommend postural exercises and stretches which help promote the better posture.
    Now it could be argued that there is a neuromotor effect here, but I do not feel it is exclusive of a mechanical effect. The patient has to overcome force which is pushing them into the pathological state... perhaps causing neuromuscular dysfunction??? This must be first changed mechanically- or at the very least will be more difficult to change without looking at the base mechanics.
    It drives me crazy when I hear Physios etc saying 'you don't need orthotics- just do this exercise for a few months'. Perhaps better to do the exercise and address underlying mechanical issues?

    In addition, I do not see that a neuromotor effect must mean more muscle activity- it may mean altered activity which may be more efficient. Is that not reasonable?
  18. Charlie Baycroft

    Charlie Baycroft Active Member

    If you look back to the definitions that Kevin proposed you will see that he refers to direct mechanical effects. IMHO a device would have to have some contact with the body in order to have a DIRECT mechanical effect.
    If you are referring to the fact that something was in contact with the body for a variable period of time and that there are residual effecs as a result of this contact then these residual effects are more likely to be neuromotor consequences of that direct mechanical effects.

    Of course there is a mechanical element to anything one would care to mention even the continual impact of subatomic particles (neutrinos and quarks) on the body all the time. We live in a physical world.

    When I think of mechanical effects I do so in terms of mechanical principles from physics, forces, vectors, moments, force, power, action reaction, etc. Mechanics is governed by a set of rules and the results of mechanical effects should be consistent with those rules. So the result of applying a specific force to a segment of the body should be predictable by those rules and when the force is removed, the effect should cease.

    Cadaver specimens are probably the best medium for studying the mechanical effects of orthoses on the lower extremity because neuromotor mechanisms are not acting in dead legs. However, one has to also have studies of the effects of various orthotic modifications in vivo because the patients are (hopefully) alive.

    Living systems are more compicated because of the neural and motor elements and also because of the effects of consciousness on the function of nerves and muscles.

    Say that I have my gait analysed and the report states that I have certain undesirable movements of the rearfoot (hyperpronation persisting through midstance and almost to the end of propulsion). Now I read Root Orien and Weed and come back for re-analysis and my gait is theoretically perfect. By what mechanism was this change mediated?

  19. CraigT

    CraigT Well-Known Member

    I think this is what he was referring to when Rutherford said 'Science is either Physics or stamp collecting'
  20. Charlie Baycroft

    Charlie Baycroft Active Member

    Good quote. Didn't know Rutherford made orthotics. Lol.
    The is no denying that orthoses have direct mechanical effects on the sole of the foot and throughout the body.
    The neuromotor responses to these effects ar also real and significant but less well appreciated.
    I am not suggesting that we abandon out biomechanical knowledge in favour of a new model (fad). But, we can augment our undertatandng of orthotic therapy by learning more about the neuromotor aspects.

  21. Jeff Root

    Jeff Root Well-Known Member

    Interesting timing for me to come across this thread. Earlier today I casted a patient for orthoses and I was wondering about this very subject. The patient has plantar, lateral foot pain on his left foot and develops leg pain (anterior tibial region) daily in the afternoon after ambulating. Watching his gait, his anterior tibial appears far more active on his left side and he has delayed loading of the medial forefoot and his hallux stays dorsiflexed for and extended period of time.

    What makes this case so interesting is the history. He was a competitive motocross rider who had a near fatal accident about four years ago. He coded on the race track and several times and while being airlifted to a trauma center. He sustained a massive head injury and was not expected to live. After being in a comma for a week or more, he regained consciousness and ultimately when through extensive speech and physical therapy. If you observed him today, you would not be able to detect any physical or mental deficit and he leads an active life as a heating and air contractor.

    The accident left him with an inability to sense where his left foot is in space. In order to climb a ladder, he has to watch his foot to confirm it is on the rung of the ladder. When he runs, he lacks confidence and tends to watch his left foot as it plants the ground. However, he has good tactile sensation on the plantar surface of his foot. He has hallux limitus on the opposite side but a reasonable range of dorsiflexion on his symptomatic foot. Biomechanically, he is otherwise unremarkable.

    He gets relief from OTC devices but it doesn’t last once the devices have been used for about a month due to breakdown of the devices. Given his neurologic history, I was wondering if his OTC devices might have a propreoceptive component which could be related to their shape or if it is purely a mechanical influence. It will be interesting to see how he does with custom orthoses and to see if the relief lasts as compared to his OTC devices.
  22. Dananberg

    Dananberg Active Member

    Great topic.
    Charlie wrote “Pain can be caused by a sustained posture that overstimultes mechanoreceptors and activates Wide dynamic range cells in Lamina 5 of the dorsal horn of the spinal cors to transmit the stimuli recieved from them to centres in the brain that percieves them as pain. Thus pain can be felt where there is no tissue damage, inflammation or presence of pain peptides. Such pain can be rapidly resolved by any modality that reduces the tension in the tissues that is overstimulating the mechanoreceptors.”
    I believe that this is the crux of understanding pain perception and FO’s. The wide dynamic range cell (WDR) is the location of both peripheral mechanoreceptors and nociceptors synapse with the spinal cord. The abnormal over stimulus results in a lowering of the threshold at which nociception is perceived. Pain and motion are essential confused at the level of the spinal cord. This is why a change in motion pattern via the use of FO can be such an effective treatment. It is also why I have advocated for the sagittal plane perspective vs. the classic motion control approach. Limiting ROM may not be as advantageous as permitting motion in the direction of movement.
    We have all had the experience, for instance, when you hit your thumb. The natural response is to shake the affected hand. The stimulation of the mechanoreceptors appears to diminish the pain sensation. This is an example of the inexorable link between motion and pain. Normal mechanoreceptor stimulation reduces pain sensation.
    The process of walking creates a very predictable series of motions in the joints of the lower extremity. These motion patterns change as single and double support phases are started and terminated. When limitations to sagittal plane motion are restricted at the foot level, compensations occur more proximally with reductions in the normal extension pattern during the single support phase. This ultimately becomes what Simons and Travel referred to as “perpetuating factors” in chronic pain patients. The abnormal pattern alters how the body “senses” pain, with exacerbation being directly related to these motion limitations. Once motion returns to a more normal extension pattern, the CNS can “reset” its sensitivity to pain and the “confusion” between what is moving and what is hurting resolves.
    Zimmermann, M, Pain Mechanisms and Mediators in Osteoarthritis, Seminars in Arthrities and Rheumatism, Vol 18, Suppl 2 1989, pp22-29
    Dananberg, HJ, “Gait Style and Its Relevance in the Management of Chronic Lower Back Pain”, In Proceedings, 4th Interdisciplinary World Congress of Low Back & Pelvic Pain”, Ed, Vleeming, A, Mooney. V, Gracovetsky, S, Lee, D, etal, November 8-10, 2001, pp 225-230

  23. Charlie Baycroft

    Charlie Baycroft Active Member

    Great to "virtually" meet you at last. I hope to have this priveledge in real life one day as well.
    Foot Orthoses (in term of the classical definition of a customized device) are an amazing form of therapy with vastly underrated potential to relieve discomfort and improve lower extremity function.
    Most people have approached efficacy only from the perspective of pain relief and, IMHO, this leads to an incorrect assumption that function has been improved because pain was relieved.
    Any shoe modification that alters motion or kinetics has a high potential to relieve pain which is independent of its effect upon the function of the lower extremity. This can be understood in terms of the tissue stress theory or the neurological mechanism that you described in your post. Perhaps there are other mechanisms as well?

    I keep trying to seek a better understanding of the effects of orthoses on the function of the lower extremity because I realised long ago that it is easy-peasy to put something in the shoe and adjust it a little so as to make the patient's pain go away. In this regard, foot orthoses are superior to any other therapy I have ever used. Easy, safe and predictably relieving the patient's immediate problems.

    I have also noticed that you can move pain around the lower extremity with orthotics and have sometimes joked that an Podiatrist could releive one problem but cause another and keep the patient coming back indefinitel if he/she was so inclined.

    IMO, we are beginning to learn more about the potential for FOs to alter neuromotor function and will learn more in the future and this will enable Podiatrists to make devices that have even better effects on the function (mechanical and neuromotor) of their patients' lower extremities.

    At the moment, however, there is some resistance to even acknowledging that FOs do have neuromotor effects on function and this will have to be overcome before we progress further.

    Discussions such as this may be helpful in promoting this awareness.

    Very best regards
  24. Charlie Baycroft

    Charlie Baycroft Active Member

    This is a very interesting case and I am not sure of the Neurological diagnosis but am looking up some info in order to hazard a guess. What I am suspecting is that he has some damage in part of the brain that is impairing his ability to detect the spacial orientation of his leg. I wonder how this would not create some changes in the pattern of gait.
    Orthotics may well releive the pain in his left foot but I would prefer for him to have a better diagnosis. Has he been re-assessed by a Neurologist about this?
    If I were you, I would get him assessed by a Neurologist before prescribing the devices. The main reason for this is that, if he has a significant central lesion and tells the specialist you gave him orthotics to fix it, this is likely to provoke an unkind response from the specialist about your knowledge and motivation in treating him. IE, "why would someone provide expensive orthotic for a CNS lesion".
    Of course, we understand that you are trying to alleviate the pain in the foot but my suggestion would be to make sure that the patient understands this very clearly and also that he needs an accurate Neurological diagnosis.
    I think it is old but still valid that proper thorough diagnosis should preceede treatment.

    Not criticizing what you are doing with the foot in this.

    Best regards
  25. Jeff Root

    Jeff Root Well-Known Member


    This patient was referred to me by both his podiatrist and his GP for functional orthoses. I own a lab and I'm not a podiatrist but I do have extensive experience in bio eval and orthotic therapy. Apparently they both felt based on his positive response to OTC devices that he would likely benefit from functional orthoses. Although this individual is an acquaintance of mine, I don't know why his podiatrist didn't treat him directly. I’m not charging for my services other than our normal lab fee for his orthoses. While he obviously has some neurological deficit, he is no longer receiving treatment for the accident and he is only attempting to resolve his foot pain.

    His condition puts him at risk given his occupation. The day before he came in for casting, he had fallen off a roof because he lost track of where his foot was. He has sensation on the plantar surface of his foot but he can’t determine where his foot is in space. He says “It’s weird, I have to watch my foot to know where it is”. While he can walk fine, he is at risk of falling on irregular surfaces or while doing other tasks. He fell of the tailgate of his truck while unloading it because he had to step onto a loading platform but he has no idea how or why he fell other than his foot must have missed the platform.

    I have never dealt with anything like this before. I think his foot pain is due to mechanical overloading of the lateral column due to delayed loading medially. I attribute this to prolonged activity of the anterior tibial. Since he doesn’t have any osseous condition that would cause mechanical overloading of the lateral column, I’m thinking his OTC orthoses might be increasing his propreoceptive “awareness” of GRF medially, thereby reducing activity of the anterior tibial and allowing his medial forefoot to load more normally. This is just speculation on my part and I’m open to other suggestions. I will be dispensing his orthoses next week.

  26. Dananberg

    Dananberg Active Member

    If I stick a finger with a pin, there is a mechanical response; a hole in the finger, a neurological response; it hurts, a neuromuscular response; a withdrawal, and an immunologic response; cell migration to heal the site and block infection. It would be impossible for me to fathom that when a FO is used in a shoe, there is not a similar and comprehensive effect involving multiple bodily systems (perhaps without the immunologic one…but who knows).
    During my many years of in-shoe pressure analysis use, I was struck by the force/time graph patterns with vs. without FO’s. Prior to any orthotic intervention, the one constant was a leveling of these curves during periods of time when their slopes should have been steepest. Constant force (ie, leveling of the curve slope) is related to an absence of motion (ie static position during periods of required movement). This restriction occurs irrespective of foot shape (cavus, planus or any shape in between). Moving the center of body mass from behind to ahead of the weight bearing foot/limb is the single least common denominator in gait. Failures of this movement, even for brief periods of time, results in a need to either store or dissipate the power created which ultimately produces this movement. The appearance of specific foot motions present during this act of dissipation is dependent on foot shape. The reason they occur, however, is in my way of thinking, more significant that the actual motion. By specifically designing a FO to permit the body to advance over the foot, the visible motions (can be read as late phase pronation) will often resolve as this is a “result”…and not a “cause”.
    Causes of restriction may be mechanically based, ie functional hallux limitus, or ankle equinus, painful plantar lesions, arthritic joints, etc. Not all respond will respond to a FO, but require a combination of approaches including manipulation, mobilizations,resolving Tp’s in muscles, reductions in inflamed and painful sites. When understood in the context from which they are generated, solving the clinical dilemma with which these patients present is the ultimate challenge. Recognizing the complex neuro-mechanical conundrum and then addressing the issues which cause it to develop has worked best for my patients.
  27. Jeff:

    Sounds like your patient has lost the part of his cerebral cortex that recognizes joint position for the left foot and ankle. One thing that you can have him do is to try to tape his ankle, such as you would for prophylactic taping in basketball to prevent ankle sprains, which may increase the pull on the skin of the foot and ankle when the left ankle/foot moves to different positions. This increased tactile sensation from the tape on the skin that responds to ankle movement may allow him to develop better awareness of his foot/ankle position while performing weightbearing activities. I've never tried this technique, but from my understanding of the physiology of the central nervous system, this theoretically could work quite well for him over time.

    Hope this helps.
    Last edited: Jan 10, 2009
  28. Charlie Baycroft

    Charlie Baycroft Active Member

    I am not disagreeing with what you are trying to do to try to help this person with his foot pain and compliment you for caring enough to do this.
    As Kevin suggests and I agree, he seems to have a neurological defecit which may or may not have been properly assessed and this is putting him at risk of falling and seriously injuring himself. Perhaps his GP has already arranged for a Neurologist to assess this and perhaps not. If I were his GP, I would because without a specialist assessment and possibly some further investigtion we do not have a precise diagnosis and do not know the prognosis. Does the GP realise that he has neurological sequelae of thehead injury that are causing him to fall off roofs? I may be too cautious but always want to have the best possible understanding of patients' problems rather than assuming that they just have to be accepted. Getting a proper diagnosis often involves persistence in being the patient's advocate and getting the proper specialist to assist with the diagnosis.

    I would tell your friend that, if there has not been a precise explaination from a Neurologist about this loss of spacial orientation of his leg he should request further assessment and perservere until there is one. In the mean time good luck with reieving the foot pain for him

    Best regards
  29. Dananberg

    Dananberg Active Member

    Hi Jeff,

    It took me a few days to get to your message. I see this type of problem regularly. These are interesting cases and I would like to offer a different perspective on his symptoms and treatment.

    Lateral column overload is often due to an inhibited state of the peroneals. It can occur following even a very minor ankle sprain, and unless you are specifically looking at inversion muscle strength...its easy to miss. The posterior tibial will only rarely be affected by the original injury, and therefore overpowers the inhibited peroneals creating a laterally based overload (inversion). One of the common substitutions I see for peroneal inhibition is anterior tibial activity during stance phase. Prehaps related to their common insertion at the met/cuneiform joint, there are a wide variety of overuse situations which frequently develop by using a swing phase muscle repetitively during stance.

    I treat this with manipulation of the ankle and cuboid. Results are fast and generally long lasting. The orthotic should NOT be posted in the rearfoot beyond neutral, as inverting the foot will only exacerbate symptoms. Patient should be evaluated for functional hallux limitus, with an appropriately sized 1st ray cutout added. The last consideration would be LLD...with a heel lift possibly necessary. I like to watch arm swing...the arm that swings the greatest often is on the shorter of the two limbs.

    The manipulations and muscle tests can be viewed at www.vasylimedical.com (follow the links to the articles). I am a paid representitive of Vasyli.

  30. Charlie Baycroft

    Charlie Baycroft Active Member

    Dear Howard
    I find it interesting that you use manipulation. I am also a manual thrapist and many patients have restrictions in the joints of the foot that should be released by manual techniques before prescribing orthotics. The mechanism of joint restirctions is also a bit of a mystery and people looked for a mechanical obstruction for a long time before realising that manual therapy actually has a neuromotor effect in releasing some muscle tension that is blocking the ROM of the joint and displacing its neutral position.
    As you mention, ankle sprains frequently induce restricion in the ROM of the joints about the Cuboid and this also alters the alignment of the pulley for Peroneus Longus.
    Other commonly effected joints appear to be those of the 1st ray, the Talo-crural joint and the STJ. Forefoot and rearfoot alignment can be quite different before and after manual therapy.
    Do you routinely examine the joints of the foot for restrictions (somatic dysfunction) and mobilize these prior to prescribing foot orthoses?

  31. Dananberg

    Dananberg Active Member


    While I don't do anything "routinely", I do carefully exam foot joint ROM prior to casting for CFO. In my way of thinking, it makes no sense to fabricate a custom device on a cast made on a foot with one or more restricted joints. The most common manipulations I perform are of the ankle and cuboid. These both have profound neuromuscular effects and can change the shape and motions of the foot immediately upon completion. While I do have to occasionally adjust the orthoses I prescribe, it is certainly more the exception than the rule. I also use very low or no wedging effect on rearfoot posts. After measuring thousands and thousands of pre and post orthotic F-scan (in shoe pressure measurements), I have come away with the following realization. Posting based on the "visible" changes (ie, reduced pronation) within the foot leads to excessive correction. From my experience, by the time you see the change...you have likely overposted to cause it.

    Of all the "tools" I have...manipulation is the single most effective method of treating foot and lower extremity dysfunction.

  32. Charlie Baycroft

    Charlie Baycroft Active Member

    I definitely have had similar experiences. My theory is that our modern "pavements" and shoes induce adaptive postural and dynamic dysfunction throughout the lower extremity. These adaptive dysfunctions include overpronation/delayed supination, joint restrictions, muscle imbalances and dysfunctional motor patterns (including dysfunctions of core structures). The stimulus for these adaptive dysfunctions is mechanical but the adaptations are primarily neuromotor.
    What you are saying about over-correction is compatible with my opinion that with FO's our aim should be to create an interface between the foot and modern environment that is more like the natural environment that we evolved in and functioned successfully in as a species (HOMO) for almost 2M yeas before the development of modern pavements and footwear.
    IMO, attempting to "control" the foot to function in a specific theoretical way can also create an unnatural environment under the foot and contribute to continuing dysfunction even though presenting symptoms are relieved.
    I find Benno Nigg's theory that the concept of comfort describes what we feel subjectively when function is natural and efficient very logical. Unfortunately, comfort is difficult to quantify and measure in scientific studies. However individual patients definitely know what is comfortable and what is not.
    Manipulation is a good example in which patients definitely experience a feeling of comfort when a restriction has been mobilized. I have also noticed this when theoretically minimal orthotic adjustements are used and patient's describe feeling immediately "different" but better.
    The realisation that FOs can act effectively by altering kinetics and neuromotor function, without apprecably having to change motion, seems like progress to me.

  33. krome

    krome Active Member

    Happy New Year to everyone. Excellent discussion so far.

    We have recently undertaken a study looking at the impact of three textured insoles on postural sway and EMG lower limb muscles in healthy older adults. Three textured surfaces were chosen on the basis that their variety of indentation and thus, the degree to which each textured pattern depressed the skin on the plantar surfaces of the feet, may bring about differing effects on postural sway and lower limb EMG activity. All three textures investigated have been used in previous research within our laboratory to determine their effect on; postural stability in middle-aged females [1] and postural stability and lower limb muscle activity in healthy young adults [2].

    The study used a within-subject experimental design with participants taking part in testing in each of three textured insole conditions. The dependent variables were anterior-posterior (AP) postural sway range (mm), AP postural sway standard deviation (mm), ML postural sway range (mm), ML postural sway standard deviation (mm), Centre of Pressure velocity (m/s) and average integrated EMG (unit) for each of 5 dominant lower limb muscles. 50 participants (29F, 21M) took part in the study.

    The results demonstrated, changes observed in the magnitude and velocity of the Centre of Pressure velocity during quiet standing with eyes closed were not accompanied by significant alterations in the amplitude of EMG activity in any of the five lower limb muscles. We concluded that the lack of a significant muscular response from healthy older adults to enhanced sensory input may be attributed to age-related changes previously reported in skeletal muscle including; a decline in proprioceptive function of the quadriceps; slowing contraction rate in the ankle dorsiflexors and plantarflexors; and increased passive resistance of connective tissues. We are now investigating older adults with a history of falling using the same textured insoles.

    1. Wilson, M., Rome, K., Hodgson, D. & Ball, P. (2008) Effect of textured foot orthotics on static and dynamic postural stability in middle-aged females. Gait & Posture, 1, 36-42.
    2. Hatton, A., Dixon, J., Martin, D. & Rome, K. (2008) The effect of textured surfaces on postural stability and lower limb muscle activity. Journal of Electromyography and Kinesiology [in press].
  34. Lawrence Bevan

    Lawrence Bevan Active Member

    Can anyone tell me me how this theoretical information in this discussion changes my orthotic prescriptions?
  35. Graham

    Graham RIP

    Lawrence wrote:

    It won't. Unless you are prepared to accept some of the minor floors with in-shoe gait analysis and actually start testing and analysing the data within the various theroretical frameworks. Something our esteamed theoretical clinical observers and commenters appear to be "afraid" to do!

  36. Graham:

    First of all, are you also afraid to do and publish research? Maybe I just haven't ever seen it, but I don't remember ever seeing your name on any published research. Is fear the only reason why valuable research is not performed by busy clinicians?

    Secondly, when has in-shoe pressure analysis had only minor problems associated with it? How do you determine the kinematics and kinetics of gait and internal loading forces within the foot from in-shoe pressure analysis? Or am I missing something here?
  37. Graham

    Graham RIP


    Your missing something. The determination that kinematics and kinetics of gait and internal loading forces within the foot are the primary pathology has not been demonstrated. What has been demonstrated, with in-shoe force measurement, that by improving timing of events, COP progression etc that local foot and global postural symptoms are improved as well, without creating a secondary compensation elsewhere.

    Not fear of doing research, fear of doing valuable research!

    Any jobs out there for a poor Canadian Podiatrist willing to subvert the profession with some "valuable" research?

  38. Graham

    Graham RIP


    Journal of the American Podiatric Medical Association, Vol 90, Issue 7 346-353, Copyright © 2000 by American Podiatric Medical Association


    Effectiveness of various materials in reducing plantar shear forces. A pilot study

    M Curryer and ED Lemaire
    Sandy Hill Community Health Centre, Ottawa, Ontario, Canada.

    Vertical plantar forces are known to be a major precipitating factor in the development of foot pathology. It is also postulated that shear forces are important in the pathogenesis of foot ulcers in patients with diabetes mellitus. Various materials are used in insoles designed to reduce forces on the foot. While many foam materials have been tested for their ability to dissipate vertical forces, few studies have tested the effect of these materials on shear forces. This study assessed the effectiveness of five different materials in reducing plantar shear forces and compared two new gel materials with three of the more conventional foam materials. Four subjects were tested while walking over a force platform with one of the five materials taped to the surface. Peak force, impulse, and resultant shear force data were analyzed. The gel materials were significantly better than the foam materials at reducing shear forces. Thus the use of gel materials in insoles may be indicated for the reduction of plantar shear forces on the diabetic foot.

    Graham Curryer mentioned in the Acknowledgements - I was the research assisstant!

  39. Graham:

    You are mistaken again. Please show us research evidence that supports your statement:

    "What has been demonstrated, with in-shoe force measurement, that by improving timing of events, COP progression etc that local foot and global postural symptoms are improved as well, without creating a secondary compensation elsewhere."

    And secondly, I, and nearly all the other talented clinicians I know, have never used in-shoe pressure analysis in treating our patients with foot orthoses, but we all get very good results with foot orthoses. Why then is in-shoe pressure analysis a requirement to get good results with foot orthoses that don't cause "secondary compenstions" elsewhere? The research evidence certainly doesn't support your contention that in-shoe pressure analysis is a requirement to treat patients effectively. Or is this just another guess from a poor Canadian research assistant??:rolleyes:
  40. Graham

    Graham RIP


    Sadly, if you don't use it you will never know what else your orthoses may be doing! Are you making the dynamics different or better. You will never know. If I give a person with a broken arm morphine his pain goes away yet it doesn't fix the arm and may cause him to injure it further!


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