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Knee flexion with heel raise

Discussion in 'Biomechanics, Sports and Foot orthoses' started by baton de colle, Feb 22, 2010.

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    Hi all,

    I’m a podiatry student and have been looking at knee flexion and how it changes when a 10mm heel raise is introduced (ipsilateral side). Most of my subjects are showing the increased flexion at midstance (tibia vertical) as expected. However, a surprisingly large portion of subjects are showing a decrease in flexion.

    This is as a mean of 10 trails so I am reasonably convinced that the decrease in flexion is actually occurring but I’m not clear in my understanding as to why.

    My current reading is implying the presence of an equinus or hallux limitus but I’m not overly clear in my understanding as to why these pathologies would be causing this.

    I would greatly appreciate it if someone could clarify why these reductions in knee flexion are occurring.

    Thanks all

  2. Hi Carol,

    Read the below thread don´t read to much into the 1st post or two but I think 5-6-7 will help you out.


    Basically its all to do with the difference between internal and external moments acting on a joint.

    Gastroc-sol contract internal plantarflexion moment at the talocural.

    Gastroc contract internal flexion moment at the knee.

    An internal plantarflexion moment at the talocural joint will increase the GRF ( Ground reaction force ) Vector at the forefoot which among other things will cause an increase external knee joint extension moment.

    So with your heal lift you get an external plantarflexion moment at the talocural joint, which increases the GRF under the forefoot which will increase the Force vector of the external knee extension moment at the knee which will lead to the reductions in knee flexion that you have seen in your experiment.

    Hope that helps
  3. Hi Michael,

    Thanks for your help.

    If I’m following this through right, would be it be due to the position of the STJ axis of motion as to which occurs?

    If the STJ axis is laterally deviated would you be more inclined to see the external rotation at the knee and decreased flexion. Thus with a medially deviated axis an internal motion which increases knee flexion?

  4. Hi Carol

    The 2 axis which I would think about 1st are the talocural and the knee. The STJ axis position I would not consider so important.

    If your question why do you see the knee change in some as not in others, is a hard question answer as the answer may be different for each person.

    Think about which muscles cause internal flexion and extension moments at the knee, if the flexion muscle are weak in some people then the GRF vector from the forefoot will have a greater effect-- external extension moment at the knee. Muscle length will also play a role here as well.

    Also look at the last 2 posts on that thread I recommended above , we were trying to be a bit funny but consider what other things may increase the GRF under the forefoot.

    People with a more forward COM (centre of mass) such people with a belly or pregnant as an example.

    So as David Smith said if the position of the hands is forward you may get a increase in GRF vector under the forefoot as well, there are many many variables what you need to find out is what they are from person to person.
  5. Hi Michael,

    My subjects showing external rotation are all normal to low on the BMI (not the best measure I know). But, there doesn’t seem to be any anterior shift in the COM other than that caused by the heel raise which was used in all of the subjects. Am I right to be looking at STJ axis orientation or should I be looking elsewhere for a reason for the difference? I’m only seeing external rotation in subjects with more adaptable foot types.
  6. Ok so we have moved on from extension moments at the knee from your 1st post. To external rotation...... Now the stj axis comes into play. Heres a quote from Craig Payne which might answer some of your questions.

    and you may have already have found one other answer FHnL, which will lead to reduced windlass mechanism.

    As for the questions of if they will always occur at the same time I´ve no idea maybe some else will be able to help,but as for a guess it will depend on the directio of the forces and will be different from person to person
  7. David Smith

    David Smith Well-Known Member

    Carol, What Michael has a said is quite true i.e. in some cases a heel lift may move the CoF/CoP anterior on the plantar foot and so, via the GRF vector, induce an increase in the external knee extension moment.

    If the subject had an ankle joint that was stiff to GRF (ankle or forefoot equinus) then in this case it may be quite likely that the CoF would move posteriorly and reduce the external knee extension moment. If the ankle had good RoM then at some point a heel lift may tend to move the CoF anteriorly. The higher the heel lift the more likely this is, imagine a very high pair of stiletos. In this case it may be a matter of choice as to the actual kinematic action of the knee during stance phase of gait. If you think about girls wearing high heels, then some you will notice walk with very flexed knees and others with an extended knee and use the pelvis rotation in the transverse plane to attenuate shock.

    http://www.videojug.com/film/how-to-walk-in-high-heels ;)

    If you imagine that in normal stance the reference position of the plantar foot to the tibia is 90dgs. If you were to raise the heel but keep this 90dg relationship then you would tend to fall on your face. To avoid this you must move or keep the CoM over the foot. To achieve this you can either choose to bend your knees or you can choose to keep extended knees and hips or you could flex the hips and increase the lumbar lordosis.

    To determine the change in kinetic action of the heel lift on a certain subject of interest it is optimal to assess them walking over a force plate and observing the GRF vector with and without heel lift.

    The higher the heel the higher the forefoot-pressure in ten healthy women

    Caroline M. Speksnijdera, Rieny J.H. vd Munckhofa, Sjors A.F.C.M. Moonenb and Geert H.I.M. Walenkampa, ,
    aDepartment of Orthopaedic Surgery, Academic Hospital Maastricht, P. Debeyelaan 25, 6229 HX Maastricht, The Netherlands
    bFaculty of Medicine, University Maastricht, The Netherlands

    Available online 23 February 2005.
    Foot pressures were measured in 10 healthy women, while walking in high-heeled (5.91 ± 1.03 cm) and low-heeled (1.95 ± 1.06 cm) shoes. The foot was divided into seven regions. For each region the following parameters were calculated: the peak pressure (PP), pressure time integral (PTI), maximum force (MF), force time integral (FTI), contact time (CT) and contact area (CA). In high heels loading was reduced in the midfoot and under the heel, the CA and MF were decreased significantly. Walking with high-heel shoes caused an increase in peak pressures of 30% in the central forefoot (metatarsals 2–4) in comparison with low heels, whereas PTI increased by 48%. In the medial forefoot (metatarsal 1) these parameters increased by 34% and 47%, respectively. An increasing heel height shows a correlation (>0.70) of PP to PTI in the medial forefoot and to PP in the central forefoot.
    Keywords: High-heel shoes; Foot pressures; Insole measurements

    Effects of Heel Height and Shoe Shape on the Compressive Load Between Foot and Base
    A Graphic Analysis of Principle

    Nana Lise Broch, CPO, BSc * , Thomas Wyller, MD and Harald Steen, MD, PhD
    * Prosthetic and Orthotic Programme, Faculty of Health Sciences, Oslo University College, Oslo, Norway.
    Sophies Minde Orthopedics Ltd, Oslo, Norway.
    Biomechanics Laboratory, Orthopaedic Department, Rikshospitalet University Hospital, Oslo, Norway.

    Corresponding author: Harald Steen, MD, PhD, Biomechanics Laboratory, Orthopaedic Department, Rikshospitalet University Hospital, N-0027 Oslo, Norway.


    Even in the ever-changing and increasingly technical realm of medicine, commonsense approaches are needed. We can still learn from our predecessors by using their practical and simple methods. In this article a graphic approach in the sagittal plane is used to explain the relationship between the heel height of a shoe and load under the foot. By using an elementary theoretical model based on schematic sketches, an analysis of principle can be performed to calculate the change in the distribution of mechanical stress in the planta with change in foot orientation. The model shows that when standing posture remains unaltered, load under the forefoot increases and load under the heel decreases with elevated heel height and the corresponding changes in shoe shape. These results can be confirmed by pedobarographic and gait-analysis measurements, but the graphic method can be used without application of advanced instrumentation. The rationale behind the model is to use common terms and simple means to facilitate a more fundamental understanding of complex mechanical orthopedic problems. The method is meant to be a helpful supplement to clinical judgment in the many situations in which advanced instrumentation is not available. (J Am Podiatr Med Assoc 94(5): 461–469, 2004)

    The Effect of Heel Height on Gait and Posture
    A Review of the Literature

    Emma E. Cowley, MSc *, Thierry L. Chevalier, BSc and Nachiappan Chockalingam, PhD
    * Faculty of Health, University of Plymouth, Plymouth, United Kingdom.
    Faculty of Health, Staffordshire University, Stoke on Trent, United Kingdom.

    Corresponding author: Emma E. Cowley, MSc, Faculty of Health, University of Plymouth, Derriford Rd, Plymouth, Devon, PL6 8BH United Kingdom. (E-mail: emma.cowley@plymouth.ac.uk)


    This article explores relevant full-text literature to reveal the effects of heel height on gait and posture and the kinetics and kinematics of the foot, ankle, knee, hip, and spine. Furthermore, special attention will be given to the implications of increased heel height for clinicians treating locomotor disorders and provide information to aid clinical decision making. Full-text articles accessed from databases including AMED, ASSIA, Blackwell Synergy, BNI, Voyager, CINAHL, ScienceDirect, and Taylor Francis inform the review. (J Am Podiatr Med Assoc 99(6): 512–518, 2009)

    Cheers Dave
  8. Atlas

    Atlas Well-Known Member

    Clinically, that does not stand up at all.

    Heel raise is proportional to knee flexion IMO.

    Physiotherapist (Masters) & Podiatrist
  9. CraigT

    CraigT Well-Known Member

    Nice simple explanantion Dave!

    And I must say that this
    is the most impressive bunch of surnames i have ever seen in a paper....!
  10. May seem like a strange question, but does functional hallux limitus lead to "reduced windlass mechanism"?
  11. David Smith

    David Smith Well-Known Member

    Thanks and yes now you point it out, wasn't Anthony Moonbender Specsnudger featured on a Monty Python sketch or was it Peter and Dudley http://www.youtube.com/watch?v=Kyos-M48B8U

    Cheers Dave
  12. I beleive I should say you got me.....:D considering our discussion in the auto-support thread, old habits and all that.

    Perhaps I should have said reduced Windlass mechanism from the medial band of the plantar fascia from less 1st MTP joint dorsiflexion.
  13. I think it's an interesting topic, worthy of further discussion. I know that we are supposed to believe that functional hallux limitus results in "reduced windlass function", but I'm not sure how windlass function is measured. Therefore, I don't know how we could study whether or not this function is or isn't reduced in the presence of functional hallux limitus?

    Also, is the peak hallux dorsiflexion reduced in functional hallux limitus?
  14. Dave.

    Thanks for that, i now definately have a couple of answers to my question. I will go and have another read
  15. I see your point, clinically we have

    1. no windlass
    2. increased force of dorsiflexion of the 1st MTP joint to obtain windlass
    3. normal windlass on dorsiflexion of the 1st MTP joint.

    but what is the point when increased force become normal force.

    Also we could add to that when does windlass become windlass mechanism, I think Eric said he defines that as when the arch begins to rise, but internally the windlass mechaim should be occuring before we can see a change in the foot I would think .

    As for if peak dorsiflexion is reduced I´m not sure maybe it a force thing again.Increased force to obtain the same level of dorsiflexion. Until the joint becomes Hullax rigidis.

    Also at what angle of dorsiflexion of the 1st MTP joint does the windlass effect start working and would this be different from person to person ?
  16. But what is "windlass"?
    What factors will influence "arch rising" in concert with digital dorsiflexion?
    So if we have the same level of dorsiflexion, do we have the same windlass effect?
  17. efuller

    efuller MVP

    Hi Carol,

    Are you looking for a purely mechanical explanation? I don't think you will find a purely mechanical explanation. You have to remember that there is a brain attached to the foot. That brain is going to experiment to find the most comfortable way to walk when it's environment is altered. That behavioral adaptation may be different for different people and it may change over time.

    Have you put the lift in one of your shoes and walked around for a day thinking about how many different ways you can walk differently. Is 1cm enough to make you change your gait?

    On the knee and STJ and heel lifts. The knee and the STJ are unrelated. You can pronate or supinate as you flex and extend your knee. Try it.

    On the center of pressure under the foot with heel lifts. This is a choice. Stand on a heel lift and lean forward and backwards. The location of force under the foot will change with leaning/muscle activation. Try it.


  19. Back to the 1st MTPJ are we?;)
    What about the length and orientation of the bony segments? Moreover, the radius of the metatarsal heads? I'm just building a 24" bmx bike to go racing on, the key factors are the size of the wheels, the length of the crank arms the size of the front and rear cogs- see the analogy?
    This is true regardless of "functional hallux limitus". Step to step varation in 1st MTPJ dorsiflexion is likely to occur across the population. Moreover, shoe to shoe variability will occur also. The point is that the degree of dorsiflexion of the digits should, to an extent, determine the tension in the plantar fascia, thus all other factors being equal, if we have the same degree of dorsiflexion we should have the same influence on the plantar fascia exerted by the digits. The key being: the timing may be different.
  20. How does tension in the achilles influence "windlass function"?
  21. efuller

    efuller MVP

    To expand on Simon's question. You can't have no Windlass. The structures are still there. What do you see when there is no windlass. The Windlass mechanism of the foot includes the plantar fascia and the bones of the foot and create what is known as a tied arch. When tension is increased in the plantar fascia there will be increased plantar flexion moment on the metatarsal and there will tend to be an increase in supination moment in most feet.

    How do you obtain a windlass. The anatomical structures are still there.

    I don't think that I said that. I have talked about the reverse windlass where when there is arch lowering you will tend to see plantar flexion of the hallux and there certainly is a plantar flexion moment acting on the hallux. It's all a continuum. With unwinding of the windlass the windlass mechanism is still the windlass mechanism. The forces and moments are still there.

    Hallux rigidus may be caused by repetitive high stress on the 1st mpj from forces within the windlass mechanism. However, hallux rigidus is characterized by osteo arthritis of the 1st MPJ with osteophytes and very little passvie range of motion in the unloaded foot. You can get a temporarily very stiff 1st mpj in stance caused by the forces in the windlass mechanism. I would call this functional hallux limiitus

    There is a lot of discussion about establishing the windlass. I'm not sure what means.


  22. all the talk of Fhnl got me damm

    Nice analogy, be a good teaching aid, build some crazy windlass machine with bike parts

    Due to the soft tissue connection of the achielles and plantar fascia this will be negative but there will also be and increase in the GRF under the forefoot this will be positive.
  23. I mean that as you dorsiflex the 1st you wind up the plantarfascia - obtain windlass. I see you point, how should we express it if we have negative windlass positive windlass or activation of the windlass (from your quote below)?

    This where I got that arch raise from here http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=42622

    Just as I think I´m getting my head around it all


  24. Thanks Eric.

    I confess, i normally favour the mecanical explination as thats my background. But i will have a think on the neurological factors.

    I wear a heel rasie as standard so stopped thinking about how it alters my gait along time ago. May swap it over for a while for a refresher

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