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Windlass and children feet

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Petcu Daniel, Sep 30, 2019.

  1. Petcu Daniel

    Petcu Daniel Active Member

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    In 2 older threads [ Is It Unethical to Prescribe Orthoses for Children with Asymptomatic Flatfoot Deformity? + When should we biomechanically treat a child? ] Kevin notice the difference between 'symptoms' and 'sign' [#117] while Craig make a reference to the windlass and starting of heel-toe gait pattern development [around 6 years old].
    I want to clarify myself with the proper timing of windlass mechanism function as it can be seen through plantar pressure measurement, especially through the timing of pressure on the heel, MT1-2 and hallux. Do you know any paper where this timing is evaluated?
    Second: from the point of view of Kevin, could be seen a delayed windlass mechanism as a 'sign' of gait dysfunction which could justify the necessity for foot orthotics for children with asymptomatic flatfoot?
    Any feedback will be apreciated,
    Thanks in advance,
  2. Craig Payne

    Craig Payne Moderator

    I not sure there is any direct evidence for that, but the comment was based on the heel-toe gait starting around that age, so hallux dorsiflexion during terminal stance starts around that age = windlass is starting to be used then.
  3. Petcu Daniel

    Petcu Daniel Active Member

    I would like to understand the relation between the starting of hallux dorsiflexion and the magnitude of pressure under the hallux. In some children [age aroud 6-7 years] with a moderate pronated foot posture [I know, is a vague term!] which I've evaluated on a pressure platform I've seen the pressure under the hallux is starting after heel off [pressure = 0] which seems to be a delayed windlass. How normal / functional is this? I don't have pressure distribution of children with 'normal' foot posture [probably best quantified with FPI]. In adults, the pressure graphs of hallux and heel are intersecting a little [normal] or much more [hallux rigidus].
    Do you know any literature describing the timing of loading/unloading the heel-MT1-2 and hallux in children?
  4. efuller

    efuller MVP

    Pressure under the hallux is going to be related to platnar flexion moment at the first mpj. In some feet, those that use the plantar fascia to resist pronation moment at the STJ, there will be more tension in the fascia, which will create a plantar flexion moment at the mpj.

    I've always had a problem with the idea that the windlass is "functioning" or not. The windlass is a passive structure. One "function" is to stiffen the foot. Stiffening the foot can happen without hallux dorsiflexion. The windlass can unwind with arch flattening to create tension in the fascia.

    Another "function" of the plantar fascia is to create a supination moment at the STJ. Should every foot resupinate prior to the propulsive phase of gait? Resupination was taught as the ideal normal. You can make the case that you can take a longer stride if the leg externally rotates, relative to the foot, as opposed to not externally rotating. However, we don't always want to take a longer stride and we don't always want to walk straight ahead. In feet with a laterally deviated STJ axis, when the Achilles plantar flexes the ankle it also creates a supination moment at the STJ. For this foot, peroneal contraction to pronate the STJ might be safer in terms of preventing ankle sprains. So, for this foot it might be "normal" to pronate just before heel lift.

    What a foot should "normally" do is an open question and may not be the same for all feet. This fact makes it difficult to determine what the normal windlass function should be. That said, a finding of zero pressure on the hallux before heel lift may still be a useful in terms of figuring out what is going on in the foot. When this happens the windlass is definitely not creating a supination moment at the STJ. This begs the question of whether this particular foot needs more supination moment at this point in time.

    When using pressure distribution to analyze feet you run into the problem of: Does the gait cause the pain, or does the pain cause the gait? Sometimes it's one and other times it's the other. Limping is altered gait due to pain. There is some literature stating that there is less variation of gait when there is pain. If certain motions/positions hurt, you are more likely to avoid them.

    I don't think there should be one optimal gait pattern for all feet. Different feet will behave differently.

  5. Petcu Daniel

    Petcu Daniel Active Member

    Ok, but in the particular case of a child 6-8 years old without pain [asymptomatic], moderate foot posture and having a delayed windlass [which, as I've understood, could be considered a 'sign' of gait dysfunction taking into account the Kevin's point of view ???] there is a need for more supination moment ????
  6. Petcu Daniel

    Petcu Daniel Active Member

    'moderate pronated foot posture' instead of 'moderate foot posture'
  7. efuller

    efuller MVP

    I guess you could call that a "sign" of gait dysfunction, because this child is not walking like other children. Why is this child walking different than other children? What findings are you saying is a delay in the windlass.

    Late loading of the hallux could be caused by different things. Once, you see the delay, you still have to explain why there is a delay. A partially compensated varus is an entirely different situation from someone who has "chosen" to use their posterior tibial muscle to hold the foot in a supinated position for the early part of stance phase.

    The delay in the windlass may, or may not be, sensitive for "abnormal" gait. It is certainly not specific for the cause of the different gait.
  8. Petcu Daniel

    Petcu Daniel Active Member

    In the case of a child 6-8 years old, which are in your opinion the causes for a delayed windlass?
    Will you use foot orthoses if he is asymptomatic and has a moderate foot posture ?
    If yes, why do you think the foot orthoses will be of help?
  9. efuller

    efuller MVP

    I wouldn't make my decision of whether or not an asymptomatic patient had a delayed windlass (what is the definition of that again.) I would treat symptomatic children like I would treat symptomatic adults using the tissue stress approach. Identify injured structure and design treatment to reduce stress on that structure.

    When would I treat an asymptomatic person? When I thought they had a finding that would put them at risk for developing symptoms. For example, an extremely medially deviated STJ axis is something that I believe would lead to pathology. I don't know, yet, if a delayed windlass is going to lead to pathology. There may be more than one cause of a delayed windlass. One should look for the causes of a delayed windlass that you would think lead to pathology. A partially compensated varus is something I could see treating asymptomatically. However, the finding that I would be treating is very low load on the medial forefoot and high load on the lateral forefoot in relaxed static stance (with no eversion range of motion available) and not a delayed windlass.

  10. Petcu Daniel

    Petcu Daniel Active Member

    I am tempted to answer with a question: what is the windlass?
    From a kinematic point of view means hallus dorsiflexion with plantar fascia winding on metatarsal heads having as an effect the rising of the longitudinal arch
    From a kinetic point of view means that force applied on the hallux at the proper time in gait cycle will create enough tension in the plantar fascia in order for this to achieve its 10 hypothetical functions [ http://www.runresearchjunkie.com/the-windlass-mechanism-foot/ ]
    From Craig's blog we have:
    'Delayed onset. The assumption is also that as soon as the heel comes off the ground and the load goes on during propulsion, that the windlasss should start straight away. Any delay in the windlass initiating is theoretically not going to leave the foot in a very good position to resist the loads that are just started being applied. ...", [ http://www.runresearchjunkie.com/the-windlass-mechanism-foot/ ]
    And again from the same post [hoping this is not extracted din context]:
    'I did not address the issues of the windlass mechanism in my rant on the nonsensical understanding of “overpronation”, but hopefully you can see that no amount of minimalism or barefoot running, gait retraining or muscle strengthening is going to help this foot with no or very delayed windlass!'
    The question is: How much will be of help muscle strengthening versus foot orthoses in the case of asymptomatic 6-8 years old children having moderate pronated foot posture ?
  11. efuller

    efuller MVP

    The plantar fascia is not the only structure resisting dorsiflexion moments applied to the forefoot. In the foot there is mechanical redundancy. If the other structures can withstand the load applied, then there is no problem if the winding of the windlass is delayed.

    The research junkie post described an interesting situation where a foot can be in static stance and the hallux can be dorsiflexed several degrees before arch raising is seen. There are other feet, in static stance, where you cannot lift the hallux off of the floor and in those feet you can feel the tension in the plantar fascia, by palpating the arch.

    What is happening in those feet that have some hallux range of motion before you see arch raising. Those feet are standing in equilibrium with some structure(s) other than the plantar fascia, resisting arch flattening. (The arch flatting forces in static stance are gravity acting on the body and ground reaction force.) As the windlass is wound, and the hallux dorsiflexes, there is gradual increase in tension in the fascia and decrease in tension in the other plantar structures. Finallly, the hallux is dorsiflexed enough that all the tension is in the plantar fascia and the arch raises. Is there a problem there?

    Do these feet need either muscle strengthening or orthoses? In earlier posts you were describing using the delay in the windlass as a screening tool for treatment. When you see a delay in the windlass, what problem are you trying to prevent? In the case of the foot with a functional hallux limitus where you can palpate the tension in the fascia in static stance, I can see trying to prevent pathology because I would bet theses feet are more likely to go on to structural hallux limitus with MPJ arthritis or IPJ arthritis. The functional hallux limitus feet have the problem of high loads in the fascia and at the MPJ. The feet with delayed windlass have decreased loads in the fascia. They may get high loads in the other structures, but with winding of the windlass, those high loads can be decreased.
  12. Petcu Daniel

    Petcu Daniel Active Member

    I believe it could be the problem you've described in your article - point D from the attached figure where the transverse plane effect is overcoming the sagital one. [the arch doesn't rise too much in dynamics]. The tension in plantar fascia is created later in the propulsion phase. I think this is one of the reasons for which in some children around 6 -7 years old has a moderate pronated foot posture. How can you see this in the context of these children?

    Attached Files:

  13. efuller

    efuller MVP

    For the feet, in stance, that you are able to dorsiflex the hallux more than five degrees before you see arch raising: I believe that what his happening is that they are in equilibrium around the STJ, probably with STJ ROM of eversion available and the windlass is easy to wind, because there is very little tension in the fascia. In these feet the center of pressure is likely to be under the STJ axis.

    In contrast there are feet with a more medially deviated STJ axis where the center of pressure is lateral to the STJ axis creating a pronation moment at the STJ that needs to be resisted by some internal structure. Tension in the plantar fascia can create a supination moment to resist a pronation moment from the ground. In these feet you should have immediated resistance to hallux dorsiflexion because the fascia is tight at rest.

    The situation in part D of the figure my windlass article, is a foot with a very medially deviated STJ axis because the rearfoot is adducted and the forefoot abducted. I'm theorizing that this foot will tend to have high tension in the fascia at rest (unless the medial arch is on the ground). As Jack described in his article, tension in the fascia will tend to cause further abduction of the forefoot (same thing as adduction on the rearfoot.)

    I don't think that the foot in figure D has relevance for the child with moderate pronated foot posture. When you see the foot where the windlass increases internal rotation of the rearfoot you would say that that foot has severe pronated foot posture.
  14. Petcu Daniel

    Petcu Daniel Active Member

    Why not?
    Thanks for patience!
  15. efuller

    efuller MVP

    No problem.

    Figure D was a picture of a foot with extreme internal rotation of the rearfoot relative to the forefoot and would have a very prominent talus on the medial side of the foot. This would be a finding that would push the foot beyond mild to moderate into the classification of more severe pronation. The feet in figure D exhibit internal talar rotation with activation of the windlass. These are very rare feet.

    One might think this foot type would invalidate the idea that the windlass mechanism creates a supination moment because in this foot it looks like the windlass causes increased pronation (internal talar and leg rotation.) However, you can explain the internal rotation by looking at the free body diagram forces applied to the extreme shape of these feet. In some feet the windlass creates a supination moment and in other feet it creates a pronation moment.

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