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Plantar fascia strectching - a finite element analysis of the windlass

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, May 28, 2008.

  1. NewsBot

    NewsBot The Admin that posts the news.


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    Finite element analysis of plantar fascia under stretch-The relative contribution of windlass mechanism and Achilles tendon force.
    Cheng HY, Lin CL, Wang HW, Chou SW.
    J Biomech. 2008 May 23. [Epub ahead of print]
  2. Admin2

    Admin2 Administrator Staff Member

  3. drsarbes

    drsarbes Well-Known Member

    SO........how many really think the plantar fascia can be stretched?
    MEANING...actually elongate the fascia.

  4. davidh

    davidh Podiatry Arena Veteran

    Not me.
  5. All ligaments, tendons, and fascia can be stretched, including the plantar aponeurosis. The question is not whether it can stretch or not (i.e. undergo elongation), but whether a permanent change in length can occur to the structure. Unfortunately, since both ligament and tendon are viscoelastic structures, and therefore exhibit the the time-dependent mechanical properties of creep response and stress relaxation, the time at which you measure the length of the plantar aponeurosis relative to the time and duration of its last elongation is very important.

    So, in answer to your question, yes, the plantar aponeurosis can be elongated temporarily. However, permanent elongation probably only occurs with plastic deformation of the internal structure (i.e. tearing or sliding of collagen fibers) of the plantar aponeurosis.
  6. drsarbes

    drsarbes Well-Known Member

    so, does that mean you voted yes before you voted no?
    No need to qualify the answer.
  7. Steve:

    A teacher asks two students, one a podiatrist and the other one an engineer, the following question:

    Do you think a steel rod can be stretched?

    The podiatrist answers "no".

    The engineer answers "yes".

    Which one is right??

    By the way, the elastic modulus (Young's modulus) of steel (about 200 GPa) is far below that of the plantar fascia (probably about 1.5 GPa). Which student do you believe gave the better answer?? GPA = gigaPascals
  8. drsarbes

    drsarbes Well-Known Member

    Hi Kevin:
    My point is simple, having done plantar fasciectomies there is just no way any adult is going to elongate this structure with exercises.

    If practitioners wish to dispense night splints, fine, but at least be honest with the patient and explain how stretching an achilles will help their fasciitis.

    IMO this is very basic stuff. You can spin it anyway you'd like. Some question can be answered with a simple "yes" or "no" - without qualification. This is one of them.

  9. Steve:

    Sorry, I can't agree with you. Stretch means to elongate. Research has shown that the plantar fascia elongates in response to a tensile loading force (Wright DG, Rennels DC: A study of the elastic properties of plantar fascia. JBJS, 46 (A):482-492, 1964.. In fact, research has also shown that the plantar fascia tensile force is about 0.97 times body weight during walking (Erdimir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA: Dynamic loading of the plantar aponeurosis in walking. JBJS, 86A:546-552, 2004). This means that the 250 lb patient you are treating has about 242 lbs of tensile force through their plantar fascia with every step. Are you saying that this tensile force does not stretch the plantar fascia with every step and that the plantar fascia does not elongate with every step? Why do you not think that given the known phenomenon of creep response that the plantar fascia can not elongate over time if the applied load is high enough and done for a long enough time? Do you have any research to show that the plantar fascia does not stretch??

    BTW, I also do plantar fasciotomies....just did one a few days ago.
  10. drsarbes

    drsarbes Well-Known Member

    "Sorry, I can't agree with you. Stretch means to elongate. Research has shown that the plantar fascia elongates in response to a tensile loading force (Wright DG, Rennels DC: A study of the elastic properties of plantar fascia. JBJS, 46 (A):482-492, 1964.. In fact, research has also shown that the plantar fascia tensile force is about 0.97 times body weight during walking (Erdimir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA: Dynamic loading of the plantar aponeurosis in walking. JBJS, 86A:546-552, 2004). This means that the 250 lb patient you are treating has about 242 lbs of tensile force through their plantar fascia with every step. Are you saying that this tensile force does not stretch the plantar fascia with every step and that the plantar fascia does not elongate with every step? Why do you not think that given the known phenomenon of creep response that the plantar fascia can not elongate over time if the applied load is high enough and done for a long enough time? Do you have any research to show that the plantar fascia does not stretch??"

    OK......the original question...can you stretch a plantar Fascia?
    If you think you can, then stretch on Kevin.
    Let us know how it works!

  11. Stretching has been working just fine for thousands of my patients for the past quarter century, Steve. Thanks for the encouragement.:rolleyes::drinks
    Last edited: May 30, 2008
  12. David Smith

    David Smith Well-Known Member


    How are you defining stretch, is it time dependent?

    Any material that experiences stress ie force / cross section area will suffer strain ie a change in length Lo - L1. This change in length has a time element. Most materials and especially biological materials experience hysterisis ie the unload curve over time is different from the loading curve over time. Because of visco elastic properties, especially in biological tissue, this can result in the case where L2 at zero load and zero time does not equal Lo and is greater than Lo but less than L1. This then would be a time dependent change in length or a stretch of the tissue. After some time and providing there was no strain past the elastic limit of the tissue, then L2 would displace to Lo again. Testing of bilogical tissue usually involves pre stressing of the work piece until hysterisis is negligible

    Does your definition demand that the stretch or change in length is permanent?

    I don't think that there can be a permanent change in tissue length unless there is damage resulting in plastic deformation or failure. I don't know much about the physiology of plastic deformation or the process and outcome of repair in biological tissue and collagen rich fibres in particular. Below are abstracts that may throw some light on that.

    I think that when a muscle is streched to increase joint RoM the CNS learns that it is safe to allow a greater RoM without joint damage. The viso elastic change of length is short lived but the neurological response or phsycological response (not sure which it is) has greater longevity.

    Muscle Fibre Damage and Regeneration Resulting from Surgical Limb Distraction
    Pamela Williamsa, Hamish Simpsonb, John Kenwrightb, Geoffrey Goldspinkc
    Cells Tissues Organs 2001;169:395-400

    Using an animal model of limb distraction, the extent of muscle fibre damage and atrophy resulting from distraction at two different rates (1.3 or 3.0 mm day-1) was investigated. It was found that at the high rate of distraction there was a significantly greater loss of range of joint movement and more muscle fibre atrophy and fibre damage than at the low rate. Muscle fibre damage is usually followed by regeneration. This involves the expression of the neonatal form of myosin heavy chain, which can therefore be used as an indicator of regeneration. It was found that whilst many more fibres showed evidence of damage at the high compared to the low rate, the number of fibres expressing neonatal myosin was significantly reduced, indicating the presence of a population of fibres which was undergoing degeneration without subsequent regeneration. Thus it would appear that beyond a certain rate of distraction, regeneration may be insufficient to replace contractile material damaged by overstretching. It is suggested that these fibres are replaced with connective tissue. This process may contribute to the muscle weakness and loss of range of joint movement which sometimes accompanies limb distraction procedures.


    Viscoelastic properties of muscle-tendon units The biomechanical effects of stretching Dean C. Taylor, MD, CPT, MC, USA The American Journal of Sports Medicine 18:300-309 (1990)

    Most muscle stretching studies have focused on defin ing the biomechanical properties of isolated elements of the muscle-tendon unit or on comparing different stretching techniques. We developed an experimental model that was designed to evaluate clinically relevant biomechanical stretching properties in an entire muscle- tendon unit. Our objectives were to characterize the viscoelastic behavior of the muscle-tendon unit and to consider the clinical applications of these viscoelastic properties.

    Rabbit extensor digitorum longus and tibialis anterior muscle-tendon units were evaluated using methods designed to simulate widely used stretching tech niques. Additionally, the effects of varying stretch rates and of reflex influences were evaluated. We found that muscle-tendon units respond viscoelastically to tensile loads. Reflex activity did not influence the biomechani cal characteristics of the muscle-tendon unit in this model.

    Experimental techniques simulating cyclic stretching and static stretching resulted in sustained muscle-ten don unit elongations, suggesting that greater flexibility can result if these techniques are used in the clinical setting. With repetitive stretching, we found that after four stretches there was little alteration of the muscle- tendon unit, implying that a minimum number of stretches will lead to most of the elongation in repetitive stretching. Also, greater peak tensions and greater energy absorptions occurred at faster stretch rates, suggesting that the risk of injury in a stretching regimen may be related to the stretch rate, and not to the actual technique. All of these clinically important considera tions can be related to the viscoelastic characteristics of the muscle-tendon unit.

    Cheers Dave
    Last edited: May 29, 2008
  13. Mart

    Mart Well-Known Member

    Hi Steve

    Like you I did not take this idea very seriously until recently. Now I add it consistently to my conservative care toolbox in addition to triceps surae / tendo-achilles conditioning.

    Here's more evidence to support doing this.

    The Journal of Bone and Joint Surgery (American). 2006;88:1775-1781.
    © 2006 The Journal of Bone and Joint Surgery, Inc.
    This Article

    Investigation performed at the Center for Foot and Ankle Research, Department of Physical Therapy, Ithaca College, University of Rochester Campus, Rochester, New York

    Background: In a previous investigation, eighty-two patients with chronic proximal plantar fasciitis for a duration of more than ten months completed a randomized, prospective clinical trial. The patients received instructions for either a plantar fascia-stretching protocol or an Achilles tendon-stretching protocol and were evaluated after eight weeks. Substantial differences were noted in favor of the group managed with the plantar fascia-stretching program. The goal of this two-year follow-up study was to evaluate the long-term outcomes of the plantar fascia-stretching protocol in patients with chronic plantar fasciitis.
    Methods: Phase one of the clinical trial concluded at eight weeks. At the eight-week follow-up evaluation, all patients were instructed in the plantar fascia-stretching protocol. At the two-year follow-up evaluation, a questionnaire consisting of the pain subscale of the Foot Function Index and an outcome survey related to pain, function, and satisfaction with treatment was mailed to the eighty-two subjects who had completed the initial clinical trial. Data were analyzed with use of a mixed-model analysis of covariance for each outcome of interest.

    Results: Complete data sets were obtained from sixty-six patients. The two-year follow-up results showed marked improvement for all patients after implementation of the plantar fascia-stretching exercises, with an especially high rate of improvement for those in the original group treated with the Achilles tendon-stretching program. In contrast to the eight-week results, the two-year results showed no significant differences between the groups with regard to the worst pain or pain with first steps in the morning. Descriptive analysis of the data showed that 92% (sixty-one) of the sixty-six patients reported total satisfaction or satisfaction with minor reservations. Fifty-one patients (77%) reported no limitation in recreational activities, and sixty-two (94%) reported a decrease in pain. Only sixteen of the sixty-six patients reported the need to seek treatment by a clinician.

    Conclusions: This study supports the use of the tissue-specific plantar fascia-stretching protocol as the key component of treatment for chronic plantar fasciitis. Long-term benefits of the stretch include a marked decrease in pain and functional limitations and a high rate of satisfaction. This approach can provide the health-care practitioner with an effective, inexpensive, and straightforward treatment protocol.

    Level of Evidence: Therapeutic Level II. See Instructions to Authors for a complete description of levels of evidence.



    The St. James Foot Clinic
    1749 Portage Ave.
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
  14. Dieter Fellner

    Dieter Fellner Well-Known Member


    I am interested to know what type of exercise is being promoted to stretch the plantar fascia by colleagues and those used in the papers cited above (I do not have direct access).

    If as Kevin suggests there is 240lb tensile force generated by the 250 lb patient then why stretch at all - simple walking should provide the stretch exercise - or even running when reportedly three times body weight is generated i.e. 720lbs of tensile stress. Yet often it is the high tensile 'stressed' patient who seems to get the p.f. - somehow this idea doesn't make sense.

    I m sure someone will show me the error of my way ...:morning:

    PS I have to add I have strongly encouraged the need for patients to stretch the AT/PF, for many years - 'selling' this condition as curable with some patient input, secretly I have harboured a lack of conviction about the role of stretching. And on reviews, a good percentage of patients will admit to lapses in those daily self administered exercises. A good many patients seem to be more interested in those treatments that involve less self help.

    Who routinely maintains audit outcomes to know with some degree of confidence just how many patients are helped in this way. And how can we split the outcomes when often the exercises form part of a treatment programme that can include orthotics, activity modification, shoe mods, NSAID's, icing, taping, injections, prolotherpay, ECSWT, cryosurgery, acupuncture, surgery, BMI reduction etc etc. And to add to this a pathology notorious for spontaneous resolution i.e. the last treatment / doctor gets hailed the miracle worker. And a patient may well attend more than one specialist at the same time to 'move' it along - can we rely on this information forthcoming from all our patients.

    There are also good many patients with a flexible AT complex and lack of obvious 'pronation' related findings to explain how the condition has evolved. I count myself an occasional heel pain sufferer in this category. I found a cure that works for me but I am sure not going to talk about it on a public forum ! :sinking:
  15. David Smith

    David Smith Well-Known Member


    When I prescribe stretching I am interested in keeping or improving joint range of motion in terms of compliance to applied forces. My reasononing is this:

    Usually it is the ankle joint (talo crural joint) I am interested in. Most times I mobilise the ankle, this increases the RoM by and average of 5 - 12 dgs. (Tested by active dorsiflexion of the ankle with straight knee.) I believe this allows the shank to progress more freeley over the ankle during stance phase and so reduces tension in the achilles tendon during early stance. This therefore may well reduce tension in the plantar fascia.

    If the tension in the achilles tendon is high in early stance then there may be a tendency to early heel lift. This could correlate with early dorsiflexion of the hallux and as the hallux dorsiflexes stress and strain are increased in the Plantar fascia.
    If the hallux does not dorsiflex early and so there is functional hallux limitus then this condition will also result in increased plantar fascia tension.

    Cheers Dave
  16. Admin2

    Admin2 Administrator Staff Member

  17. I am not so sure if we can say that running generates 3x body weight of tensile force in the plantar fascia. However, it seems reasonable to assume that running generates more tensile force in the plantar fascia than walking. The figure for plantar fascia tension equalling 0.97 body weight comes from a study done on walking cadavers at the Penn State Biomechanics lab. Unfortunately, since the reserchers did not simulate the mechanical actions of the plantar intrinsic muscles in their cadaver limbs, the estimate of 0.97 could be higher than what it may be in real life. This is probably the best scientific study ever done on the plantar fascia and is the only one that I know where they directly measure tensile force in the fascia in an intact foot, without simply estimating it (Erdimir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA: Dynamic loading of the plantar aponeurosis in walking. JBJS, 86A:546-552, 2004).

    There is a difference between the elongation of the plantar fascia seen during walking or running and the elongation that occurs during stretching or in using a night-splint. The difference is both magnitude and velocity of elongation (i.e. strain rate) Since we know that ligaments and tendons are viscoelastic and show the time dependent load-deformation characteristics of creep response and stress relaxation, then there is a very significant difference in the stress within the collagen fibers of the ligament or tendon when someone takes a minute to slowly stretch their plantar fascia or hours to stretch it in a night splint to elongate it versus walking and stretching it in about 0.8 seconds.

    Ligaments and tendons are more stiff (i.e. have more internal resistance to elongation) when the elongation is done faster (i.e. strain rate is increased) than when the elongation is done slower, because their load-deformation characteristics are time depedent and these materials are viscoelastic. Having a good understanding the mechanical nature of the injured tissues of our patients seems to be a very common-sense approach for clinicians that want to better help their patients by understanding their pathologies more fully. The following links are a must-read for those clinicians/surgeons that want to understand the mechanical nature of the structural components that comprise the bodies of their patients.



    Why isn't this important information taught in podiatry school???
  18. Dieter Fellner

    Dieter Fellner Well-Known Member


    As a keen athlete / martial arts student (more so) in my younger years, I can appreciate the value of slow movement and holding the stretch over rapid 'bouncy' movements. Certainly the former is more effective and less likely to cause tears and pulls of tissue.

    But, as applied to the plantar fascia, the concept that our PF needs stretching still niggles. Our 250lb patient is still applying 240lb tensile stress just standing around. And a lot of people spend a good part of their day, if not several hours, just standing around, don't they. So why no spontaneous automatic stretching? And if stretching is such a valuable asset why is it so many patients who do not stretch can still have effective resolution of PF pain.

    And just how are those therapeutically exercised patients generating sufficient tensile stress in the plantar fascia (if that is what is being advocated, in addition to the AT stretches). I am familiar with the commercial exercise aids and one or two self administered passive exercises. Sure, you can create that sensation and make the PF 'pull' - but is this generating enough therapeutic stress to stretch out this awkward structure ? A stretch which depends almost entirely on sufficient 1st MTP joint dorsal extension. A useful adjunct or just something to give to the patient to do?

    This pathology is rare in the younger patient (with the exception of high intensity activity causing acute PF) and features more in those approaching middle age.

    Perhaps the answer is in part an age related loss of elasticity in the ligament - and instead of the physiological rebound found in the younger foot, the tensile force increasingly is absorbed by the enthesis. This might explain why the spur is often associated with the FDB insertion; is this indicative of a body's effort to accommodate and absorb those newly developing stresses ?
    There are other external and internal causes that can effect a change in the effective accommodation and dispersion of foot stresses e.g. general stiffening of joints etc. in addition to the effects of A.T. tightness, cumulative effects of footwear etc.

    I will be most interested to know if anyone can cite a paper identifying age related PF changes.

    To me it seems likely there is no single cause but an aggregate of a number of factors expressed in variable proportion in susceptible individuals. And so we have a condition which often can respond to those well established treatments. And with a subgroup of patients who are resistant.

    For sure I recollect reading and discussing (and scratching my head) back in the 'school' days of the 80's (when all foot pain was cured with a rearfoot varus wedge and D-filler pad and the PMMA rigid orthoses the holy grail), but the bottom line, even now with no further studies there is not a lot to hang your hat on, and as always, many questions are left hanging. Is this enough yet to shape clinical practice ?
  19. Mart

    Mart Well-Known Member


    Most pts I see with what I diagnose as tensile stress induced or perpetuated PHP have the commonly reported symptom of pain which is worse on standing after resting, particularly getting out of bed, this will often completely resolve after minutes or hours of weight bearing. Of the people I treat with FO who do not get better, most will if doing tissue specific stretching and improving compliance of FO use to point of not standing barefoot AT ALL until better. The most plausible explanation that I can find for this is that after resting the stiffness of the PF is at its maximum, therefore effects of stress are likely to most injurious at this time, and this is consistent with reported pain and studied benefits of tissue specific stretching on rising. After a period of weight bearing the tissue will become more compliant and the microscopic effects of the same stress will likely be less injurious. In cases of insidious onset chronic PHP it would seem reasonable to suspect that that the threshold for injury may only need to be shifted a small amount to allow resolution.

    Does this sound like a reasonable explanation for your conundrum?



    The St. James Foot Clinic
    1749 Portage Ave.
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
  20. Dieter Fellner

    Dieter Fellner Well-Known Member


    I agree with the observations above, although the pain typically will return after longer spells of activity - the most acute pain (post static dyskinesia) does abate, but also many patients will state the pain never completely goes away but it is less intense.

    Well, it's as good as any hypothesis. But by what biological process would there be increased ligament stiffness with resting ? And if this should occur is this an age related phenomenon? i.e. reduced elasticity as we get older.

    I appreciate your time taking a stab at this. The key question remains, and accepting your explanation is plausible, what place is there for bolt-on plantar fascia stretching. Especially when, to be effective, there has to be an application of some considerable force. Is it just another stocking filler :santa: ? I suspect patients will not want to exercise aggressively a very sore heel. Perhaps the suboptimal passive stretching tension kind of just loosens up the tissue so when the weight bearing force is applied the pain effect is dampened. If so it is perhaps therapeutic, but not in itself curative.

    In your explanation those patients are indeed already getting the stretch from the activity, as I have postulated as a riposte to the view that there should be even more additional stretching from the patient.
  21. Dieter, Martin and Colleagues:

    First of all, I do believe that as soon as the forefoot is loaded by ground reaction force (GRF) that the plantar fascia is elongated. This is confirmed by the cadaver studies that show with forefoot loading both the Achilles tendon and plantar fascia have tension in them, with the study by Carlson showing a linear relationship between Achilles tendon tension and plantar fascial tension (Carlson RE, Fleming LL, Hutton WC: The biomechanical relationship between the tendoachilles, plantar fascia and metatarsophalangeal joint dorsiflexion angle. Foot Ankle Intl., 21:18-25, 2000; Erdimir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA: Dynamic loading of the plantar aponeurosis in walking. JBJS, 86A:546-552, 2004).

    Why do patients suffer from post-static dyskinesthesia (PSD) in the plantar heel (i.e. pain with the first few steps when arising from a sitting or lying position)? I believe this can be coherently explained by the fact that when no GRF loads are acting on the plantar forefoot, the plantar fascia is under insignificant tensile loads so it will shorten over time. I will call the the length that the plantar fascia shortens to after an hour of so of rest the functional non-weightbearing length (FNWL) of the plantar fascia. Then when the patient first stands, the shortened plantar fascia will be subjected to considerably more tensile stress as it is suddenly stretched by GRF acting on the forefoot. The fibers of the plantar fascia then exert large magnitudes of tensile force on the sensitized periosteum/subcortical bone of the plantar calcaneus which, in turn, stimulates the pain fibers that register pain sensation for the plantar heel.

    Therefore, with each step after arising, the plantar fascia will, over the next few minutes of walking, elongate from the FNWL of the plantar fascia to a new length, which I will call the functional weightbearing length (FWL) of the plantar fascia. Once the FWL of the plantar fascia is achieved by a few minutes of walking, then the magnitude of tensile force on the plantar fascia will be reduced so that it no longer has sufficient tensile force to stimulate the pain fibers in the plantar periosteum/subcortical bone of the plantar calcaneus. This assumes that the other plantar ligaments, plantar intrinsic and plantar extrinsic muscles are functioning normally to cause sufficient forefoot plantarflexion moment to resist forefoot dorsiflexion, and reduce the tensile loading force on the plantar fascia. This mechanical scenario, which can easily be modelled using a load-sharing model of the longitudinal arch, would nicely explain the occurence of PSD and the ability of night splints to help prevent PSD in many patients.

    Just the act of standing and walking will elongate the plantar fascia some. However, stretching exercises that are specifically designed to produce higher magnitudes of tensile loading forces to the plantar fascia over longer periods of time over higher temperatures probably are best at causing elongation of the plantar fascia. Again, if the stretches are done frequently, such as three or four times a day, there seems to be better clinical response to these exercises than doing them only once daily.

    We know that ligaments and tendons will stretch easier in younger animals and when the ligaments and tendons are at a warmer temperature. Older animals also have less ability to absorb and release strain energy in their ligaments and tendons without causing ligament and tendon damage. These age-related changes in ligament and tendon mechanical function occur in all of us, whether we like it or not. Immobilization also negatively effects the mechanics of ligaments and tendons.

    I don't think there are any specific studies on aging in the plantar fascia. Most of the aging studies I have seen on human ligaments have been in the anterior cruciate ligament of the knee.

    I don't believe that the stiffness of the plantar fascia at rest versus during exercise is as important of a factor unless the increase in blood flow to the foot and resultant increase in temperature in the foot that results with walking is sufficient to reduce the stiffness of the plantar fascia. I think it is more the result of the plantar fascia being stretched from the FNWL to the FWL as noted above. I estimate the difference in the FNWL to the FWL of the plantar fascia to be in the order of 2-4 mm. This should be a sufficient elongation of the plantar fascia to significantly reduce the tensile loading force within it's fibers so that reduced pain will result in the plantar heel with walking.
  22. drsarbes

    drsarbes Well-Known Member

    Hi Kevin:
    I do enjoy your posts.
    I don't think, however, that any of this shows that the planatar fascia can actually be "stretched", i.e., have it's TOTAL length increased, with simple strecthing exercises. Perhaps in nonviable cadaver tissue, if you apply enough tension on an "extracted" plantar fascia, but this does not correlate well with patients that walk (or limp) into the office.

    My bottom line, as always, is results. I'm pleased that you have great results with stretching. I just don't see the results that some here report. In fact, Heel spur resection/Plantar fasciotomy is by far my most common surgical procedure. None of these patients have had pain for less than 6 months (daily) nor have they responded to stretching/night splints/orthotics/NSAI/Cortisone injections and or Physical Therapy, rest.

    Let me know if others have the same experience or not.

  23. David Smith

    David Smith Well-Known Member


    Could this be a problem of perspective.? Say 90% of plantar fasciitis cases are resolved by conservative treatment. You in your primary role as a surgeon are, in the main, referred the 10% of cases that have not responded to conservative intervention and so you have the view that conservative therapy is not as good as its cracked up to be by others that have the primary role of first referral therapist.

    Cheers Dave
  24. drsarbes

    drsarbes Well-Known Member

    "Could this be a problem of perspective.? Say 90% of plantar fasciitis cases are resolved by conservative treatment. You in your primary role as a surgeon are, in the main, referred the 10% of cases that have not responded to conservative intervention and so you have the view that conservative therapy is not as good as its cracked up to be by others that have the primary role of first referral therapist."

    Hi Dave:
    Very possible. The majority of fasciitis I see have already been treated. Perhaps I should try and quantify the "virgin" fascia patients and determine what my success rate is without surgery.

    Sometimes we get too close, like a tree not knowing it's part of a forest!


  25. David Smith

    David Smith Well-Known Member


    As we get older say 40 - 45 yrs, collagen rich tissues suffer glycolisation so that the colagen protiens bind to each other using glucose as a catalyst and so the tissues become stiffer with age or diabetes.

    When tissues rest the collagen becomes coiled about the elastic fibres, the fibres become oblique to the long / tension axis of the fascia or tendon or ligament. The tissues absorb fluid and become shorter and thicker. My theory is that this makes a tissue which is stiffer to sudden force application, because, using the spring and dashpot (damper) theory, the dash pot, ie the fliud displacement component, is more significant in the total stiffness modulus at this time. Also the short tissue of the PF is allowed to take more tension than the streched tissue does, because the relaxed muscles have not adjusted to the relatively shorter set of the plantar vault.

    If one looks at this model more closely. We have two springs that represent the collagen (very stiff) and elastic (more compliant) tissues and a dashpot that represents the fluid displacement.

    So in the stretched or normal state the elastic and dashpot act in paralell and the collagen is in series with these two. The dash pot has an arbritary stiffness value of 6 the elastic 2 and the collagen 12. As the elastic streches it becomes stiffer but is damped by the dashpot. As the elastic stretches the collagen unwinds and becomes very significant in the stiffness modulus of the whole. However there is a point where the whole tissue is relatively compliant to an applied load especially with an extended time factor. This allows for shock attenuation.

    In the short state the collagen is more colied and the model has in effect one spring and one dashpot in paralell. However the dashpot is much more resistant (value 8) to applied force and the spring (elastic plus coiled collagen) has a value of 6 also. This gives an initial stiffness of 14 whereas in the previous example, with 2 springs and one dashpot, the initial stiffness was only perhaps 8 and rising to 20 with strain.

    Often tissues are assumed to have a linear modulus of elasticity or stiffness coefficient but this is a typical (somewhat simplified) engineering solution to resolve a non linear assumption problem.

    All the best Dave
    Last edited: Jun 2, 2008
  26. David Smith

    David Smith Well-Known Member

    Here's a diagram to show what I mean


    Does that make sense??

    Last edited: Jun 2, 2008
  27. drsarbes

    drsarbes Well-Known Member

    Thanks for the diagram, was that part of a Power Point presentation? haha

    Unless I'm mistaken, Plantar Fascia has very little (if any) elastic fibers, and the collagen are, by DESIGN, interwoven in irregular arrangement.

  28. David Smith

    David Smith Well-Known Member


    Yes just a quick sketch nothing to professional but I think it gets the message across.

    According to Wright and Rennels A Study of the Elastic Properties of Plantar Fascia(J Bone Joint Surg Am. 1964;46:482-492.) (see attached page section extract) and others I believe you may be mistaken.

    Cheers Dave

    Attached Files:

  29. drsarbes

    drsarbes Well-Known Member

    Hi Dave:
    Thanks for attaching that.
    Don't you think it's a mistake to take a structure (fascia lata, plantar fascia, tendon, etc....and put it under a load to the point of failure (breakage) and because the structure in question is "elongating" suggest that it is "stretching" - then go one step further and suggest one can do this in a patient?

    Much of this addition in length is cellular failure, i.e., breakage. You are not going to get this elongation in stretching exercises of the plantar fascia in a clinical setting.

    You can "stretch" just about anything if you add enough force, that doesn't mean, for instance, that if you and your buddy pull on opposite ends of your car each night that one morning you'll wake up to a stretch limo in your garage! (maybe not the best comparison but I couldn't resist)

    The plantar fascia is not an isolated, independent functioning structure, as anyone who has resected one knows. I still have problems relating these cadaver or even fresh specimen studies to real living patients.

    BTW: I do need to read up on the cellular structure of the Plantar Fascia. I noticed the study you sent was quite old (almost as old as me!) - to verify the collagen/elastin composition.

  30. David Smith

    David Smith Well-Known Member

    All the best Dave
    Last edited: Jun 3, 2008
  31. drsarbes

    drsarbes Well-Known Member

    Hi Dave:
    I hope you're not spending all your free time on these posts!!!!
    I do appreciate all the information.
    We may be getting bogged down with semantics. When the fascia "elongates" a couple of mm with each step, I don't consider this "stretching"....just considering the function of the plantar fascia, if it "stretched" easily it really would be quite inefficient in carrying out it's normal function.
    When I contend that it is "difficult" (at best) to actually gain length in the plantar fascia with simple home exercises, I mean above and beyond what is available with biological tension. I certainly would not equate the ability to stretch a tendon/muscle unit to that of the plantar fascia.

    Are you having any luck with the car?????

  32. David Smith

    David Smith Well-Known Member

    Well here's some more reading that could support either side.

    Effects of 20 days of bed rest on the viscoelastic properties
    of tendon structures in lower limb muscles
    K Kubo, H Akima, J Ushiyama, I Tabata, H Fukuoka, H Kanehisa, T Fukunaga
    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    Br J Sports Med 2004;38:324–330. doi: 10.1136/bjsm.2003.005595
    Objectives: The purpose of this study was to investigate the effects of 20 days’ bed rest on the viscoelastic properties of human tendon structures in knee extensor and plantar flexor muscles in vivo.
    Methods: Eight healthy men (age: 24¡4 years, height: 172¡9 m, body mass: 69¡13 kg) carried out a 6˚ head-down bed rest for 20 days. Before and after bed rest, elongation (L) of the tendon and aponeurosis of vastus lateralis (VL) and medial gastrocnemius muscles (MG) during isometric knee extension and plantar flexion, respectively, were determined using real-time ultrasonic apparatus, while
    the subjects performed ramp isometric contraction up to the voluntary maximum, followed by ramp relaxation. The relationship between estimated muscle force (Fm) and tendon elongation (L) was fitted to a linear regression, the slope of which was defined as stiffness. The hysteresis was calculated as the ratio of
    the area within the Fm-L loop to the area beneath the load portion of the curve.
    Results: L values above 100 N were significantly greater after bed rest for VL, while there were no significant differences in L values between before and after for MG. The stiffness decreased after bed rest for VL (70.3¡27.4 v 50.1¡24.8 N/mm, before and after bed rest, respectively; p = 0.003) and MG (29.4¡7.5 v 25.6¡7.8 N/mm, before and after bed rest, respectively; p = 0.054). In addition, hysteresis
    increased after bed rest for VL (16.5¡7.1% v 28.2¡12.9%, before and after bed rest, respectively; p = 0.017), but not for MG (17.4¡4.4% v 17.7¡6.1%, before and after bed rest, respectively; p = 0.925).
    Conclusions: These results suggested that bed rest decreased the stiffness of human tendon structures and increased their hysteresis, and that these changes were found in knee extensors, but not the plantar flexors.

    Visco elastic description of collagenous tissues in simple elongation. Stromberg D et al JAP 26 6 1969

    Not possible to copy extract.

    Anyway I think the jury is out on deciding whether long term stretching of the plantar fascia is possible and benificial. I believe it is possible and you do not. I don't think we can go any further.

    However just to have the last word (possibly)

    2mm change in length in a plantar fascia 180mm long (assuming uniform cross section area) and E of 600MPa = 7Mpa of stress or about 15 -25% of limit of proportionality or a tensional force of around 210N on a PF with a CSA of 30mm.
    Quite significant I think.

    Cheers Dave
  33. drsarbes

    drsarbes Well-Known Member

    OK Dave:
    Here's MY last word......... Thanks
  34. David Smith

    David Smith Well-Known Member


    No No! I have got to have the last word:craig:

    No seriously I think this study that I had in my library may be of great interest

    Consequences of Partial and Total Plantar Fascia Release: A Finite Element
    Jason Tak-Man Cheung, M.Phil.1; Kai-Nan An, Ph.D.2; Ming Zhang, Ph.D.1
    1Hong Kong, China; 2Rochester, NY

    especially this extract

    With an intact fascia, the total tension (150 N) of the fascia
    during balanced standing was about 42.9% of the applied
    body weight and corresponded to maximal strains of 0.3%
    (Figure 5), which agreed with the experimental measurements
    in the literature.15 The maximal strains of the plantar
    fascia decreased 0.04%, 0.03%, and 0.08%, respectively,
    with medial 20%, 40%, and 60% of plantar fascia release.
    These corresponded to decreases of 16.7%, 34.7%, and 52%,
    respectively, in total tensions of the plantar fascia. With
    medial sequential release of the plantar fascia, the maximal
    strains and total tensions of the plantar ligaments generally
    increased with the sectioned portion of the fascia (Figure
    5). Compared to the intact condition, complete plantar fascia
    release resulted in an increase of about 228%, 155%, and
    72% in tensions of the long plantar (105N), short plantar
    (135 N), and spring ligaments (86 N), respectively. These
    corresponded to maximal strains of 1.6%, 1.1%, and 1.8%,
    respectively. Additional dissection of the long plantar ligaments
    enhanced the increased total tensions of the short
    plantar and spring ligaments to 296% and 134%, respectively.
    Among the four plantar fascia releases, the medial
    60% release of fascia produced the largest strains and total
    tensions on the spring ligament. However, the largest difference
    in total tension of the spring ligament between the four
    types of fasciotomy was only about 10%

    This model predicts a lot of sharing of total plantar tensional forces. A recent model that I produced predicted similar protection of the spring ligament complex by the plantar fascia. This would indicate that plantar fascia stretching induces strain in many of the plantar tissues and confounds the PF stretching debate.

    Cheers dave
  35. drsarbes

    drsarbes Well-Known Member

    Hi Dave:
    Thanks for the study (and attempt at last word!)
    Very interesting stuff. I'll have to re read this and absorb it all.
    As a note, I always perform a medial plantar fascia release with my heel spur resections. Would you predict medial arch "discomfort" post op on these patients based on this study?
  36. David Smith

    David Smith Well-Known Member


    I would predict that you do this procedure frequently and based on that assume that you do not have many poor outcomes. Therefore I would deduce that for the patients you see there is not much medial discomfort experienced post op and in the short term in particular. (how long do you follow up for?)

    Biomechanically I would predict increased stress and strain in the remaining in tact components that no longer have the protection of the sectioned plantar fascia. It is possible that this would lead to pathology and pain. This study predicts dorso-lateral midfoot pathology.

    In this study a FEA model was used and may assumptions and simplifications made, as is usual and necessary in modeling complex structures, therfore the results are characterisation based on the input data and while predictions may reasonable, reliable and accurate they may not be precise and true in terms of the real structrue. However most man made constructions are modeled in this way and bridges don't fall down and planes don't crash do they :rolleyes:

    Practically, I wouldn't know because I'm not a surgeon.

    Good discussion tho.

    Cheers Dave
  37. Steve:

    It would be hard to "predict" how a patient may respond to medial plantar fascial release, but you can be certain that there would be "increased likelihood" of certain pathologies/symptoms occuring due to medial plantar fasciotomy that can be predicted using the load-sharing model that I spoke of earlier.

    Here are the pathologies/symptoms that may occur due to medial plantar fasciotomies that are based on cadaver research and finite element modelling research:

    1. Strain in medial plantar intrinsic muscles (i.e. medial arch fatigue).

    2. Strain in plantar ligaments of medial column (i.e. medial arch tenderness)

    3. Decrease in digital purchase force in medial digits (i.e. medial hammertoe development)

    4. Increase in plantar pressure in medial lesser metatarsal heads (i.e. 2nd and 3rd metatarsalgia).

    5. Increased strain in posterior tibial muscle and possibly flexor hallucis/flexor digitorum longus muscles (i.e. PT, FHL, and/or FDL tendinitis).

    6. Increased bending moments in shafts of medial lesser metatarsals (i.e. 2nd and 3rd metatarsal stress reaction/stress fracture).

    7. Decreased supination in late midstance and early propulsion (i.e. gait finding).

    Many of these have been covered previously in my Precision Intricast Newsletter on the mechanical effects of plantar fasciotomy from June 1995 "Biomechanical Functions of the Intact Plantar Fascia"(Kirby KA: Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997, pp. 45-46) and nearly all have been supported by research evidence since my original article was published.
  38. pscotne

    pscotne Active Member

    Steel can be stretched [elongated] to some degree if enough tensile force is applied :D
  39. Frederick George

    Frederick George Active Member

    This has been an interesting thread, with a lot of theoretical models and estimates of the lenghtening of plantar fascia. I'm not sure how these apply to the original conundrum of why standing doesn't stretch the Pfascia, but stretches do.

    In the longterm study of successfully stretching the plantar fascia, was the heel spur measured, to see if it lengthened?

    Interestingly, good success has been reported from several quarters in calcaneal decompression for heel spur/plantar fasciitis pain.

    Another thought. Perhaps the typical reduction in pain after first arising could be simply endorphin release from the initial pain.

    And why are the vast majority of these patients overweight? You would think that would stretch the Pfascia even more.

    And of course, doctor bias. When you have a hammer, the whole world looks like a nail.

  40. Dieter Fellner

    Dieter Fellner Well-Known Member

    OK, clearly I am having a serious attack of ADD. Who can explain to me this apparent discrepancy of the findings? i.e. why is there such a difference in the reported tensile forces transmitted to the PF ?

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