Does genu valgum cause the foot to pronate?

This one has troubled me for a while.

When teaching the pediatrics part of the course here, especially the genu varum and genu valgum, it always comes up about the effect they have on foot function. Genu vaurm affects the foot as it has to pronate to get the foot flat on the ground. According to so many podiatric texts, genu valgum also causes the foot to pronate as the center of body weight is medial to the subtalar joint -- this has always troubled me ... how can opposite alignments at the knee cause the same affect on foot function Is this just another one of those podiatric myths

As part of the lecture, I mention this troubling aspect --- sometimes, I get the students to do this exercise:
Stand up with feet wide apart (simulated genu valgum, due to wide base of gait) -what does your subtalar joint feel as though its doing? -- the answer is always "supinating" ---- so how does a genu valgum pronate a foot, like so many podiatric texts claim??

Now thanks to Bart Van Gheluwe we finally got some real data:

Effects of Simulated Genu Valgum and Genu Varum on Ground Reaction Forces and Subtalar Joint Function During GaitBart Van Gheluwe, Kevin A. Kirby and Friso Hagman
Journal of the American Podiatric Medical AssociationVolume 95 Number 6 531-541 2005
"The mechanical effects of genu valgum and varum deformities on the subtalar joint were investigated. First, a theoretical model of the forces within the foot and lower extremity during relaxed bipedal stance was developed predicting the rotational effect on the subtalar joint due to genu valgum and varum deformities. Second, a kinetic gait study was performed involving 15 subjects who walked with simulated genu valgum and genu varum over a force plate and a plantar pressure mat to determine the changes in the ground reaction force vector within the frontal plane and the changes in the center-of-pressure location on the plantar foot. These results predicted that a genu varum deformity would tend to cause a subtalar pronation moment to increase or a supination moment to decrease during the contact and propulsion phases of walking. With genu valgum, it was determined that during the contact phase a subtalar pronation moment would increase, whereas in the early propulsive phase, a subtalar supination moment would increase or a pronation moment would decrease. However, the current inability to track the spatial position of the subtalar joint axis makes it difficult to determine the absolute direction and magnitudes of the subtalar joint moments." (J Am Podiatr Med Assoc 95(6): 531–541, 2005)

What say you?

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Foot Outcomes measures

I let my frustration show a bit here:
Another bl....y outcome measure for the foot
"Does anyone share my frustration at the plethora of outcome tools that have been developed for the foot . When will it stop? When will people actually stop developing them and start doing research that actually uses them."
" It just seems as though people are more keen to develop yet another outcome tool, rather than spend that time using the ones we have. .... why waste resources reinventing the wheel? We should be getting on with doing research on, for eg, differences in outcomes between 2 interventions using outcome tools we now have, rather than develop new tools to measure the outcomes!!"
It followed the publication of yet another tool for measuring outcomes in the foot.

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Good Feet Stores

There has been an exposure on this franchised chain of stores using hidden video camera's:
Good Feet Stores

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Mythbusting

Along the theme of the Discovery Channel's Mythbusters - Podiatry Arena has been doing some mythbusting:
The foot on the long side does not pronate more in LLD
Forefoot Varus is rare
"First Ray Hypermobility" is really bad terminology
Running shoe technology does not reduce injuries
Do foot orthoses weaken "arch" muscles?
Flat-footed 'are high achievers'
Is a calcaneal spur in the plantar fascia?
The myth & death of the hypermobile 1st ray
Good Feet Stores

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Lots of fun

Lots of fun and content at the Australasian Podiatry Council Conference in Christchurch, New Zealand. A couple of pictures and some reports here.

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Foot pronation and leg length differences

I recently posted this message at Podiatry Arena
Asymmetrical foot pronation has the potential to create a LLD of up to 1cm (based on Bill Sanner's work), so obviously this will have consequences further up the chain (esp as the pronation is also associated with internal limb rotation).

What I am talking about is a foot pronately excessively as a compensation for a STRUCTURAL LLD - something that has crept into podiatric folklore over the years.... but its just another one of those myths (...'religious fanaticism' also comes to mind, but more on that later).I certainly do not see it clinically - I see feet pronate more on the long leg and I see feet pronate more on the short leg --- I just was not seeing the foot pronating with any increased frequency in the longer leg as I was taught and as I read frequently in the podiatric literature (...funny it does not appear in the orthopaedic or physiotherapy literature ). Invariably, when I did see a more pronated foot on the longer limb, its was often easy to find another reason for it (eg asymmetrical ankle joint ROM).

I used to get tired of students coming up to me in clinic when doing a gait analysis and saying things like "Craig, the left leg is longer, but I can't see it pronating more .... "maybe because it wasn't!!!" --- but thats what they got taught and read in the podiatric literature (they don't any more)

We did 3 studies:
1. Measured RCSP and navicular height between the short and long limb in those with a structural LLD --> there were no differences
2. A subsequent study used the FPI --> no differences
3. A Pedar in-shoe comparison --> there were some functional differences between the long and short limbs, but they were not related to any asymmetries in foot pronation.

As part of this, I also did an extensive literature review and it was not surprising that there was never any evidence to support this myth in the first place!!!!! (it is an interesting case study all this!!!!) ---- in fact the opposite was the case when viewing the literature!! (I will have to add the exact refs later when in office to get them).

The first was a study published quite some time ago that looked at 3D rearfoot kinematics and found no difference between the short and long limb in those with a structural LLD.

The other study is good case of .....(I better not say it ) --- it was published in JAPMA a long time ago, but the abstract, discussion and stated conclusion of this research was clear - that the foot does pronate more on the long side in those with a structural LLD .... BUT, BUT, BUT and very very very big BUT.... the paper looked at both functional and structural LLD and if you go thru the various tables in the publication (fortunately the paper listed the info on each subject) and extract just the data on those with a structural LLD (the tables mixed them all up) and then do a paired t-test (or wilcoxon) on the data, they actually showed the opposite!!! - ie there was no more pronated foot in the long or short limbs despite their claims ---> points to huge hole in peer review process prior to publication!!!

It just does not figure that the myth continues, when ALL the evidence says it does not happen.

We did try and publish our research, but you should have seen the reviewers comments from the journal --- they found nothing wrong with our methods and analysis etc, but spit a whole lot of vitriol with a recommendation to the editor that it not be published - the review was a two page rant paraphrased as "how dare they prove something wrong that every podiatrist knows is right".... they kept referring to all the evidence that supports the concept etc etc, but never mentioned what or where this evidence is. ..... I still have the manuscript (and the reviewers comments), but just have not yet bothered to rewrite it in a format for another journal yet.

The other amusing thing is, that a couple of years or so ago this topic came up in Barry Block's PM News (Kevin Kirby might remember this), so I posted a message re our research and the lack of evidence etc etc --- needless to say, it did not go down too well (at least I do remember Kevin supporting my observations) - I even got two private abusive emails saying something like "idiot" "moron" "how dare you" etc etc ---- guess which country and 3 letters after their names that these kinds of responses come from (I wish I kept them as it would be amusing to post them here now....) ..... 'religious fanaticisim' .....

....don't you just love this kind of stuff ?

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The placebo effect of foot orthoses

We all know about the possible placebo effect of our treatments etc etc, but tend not to pay a great deal of attention to it...We have a plantar fasciitis RCT in press at the moment - subjects randomised to one of 3 "inserts" (all of which can be purchased from a retail pharmacy) - these are devices that I would never consider using clinically (they are that bad) ..... to our dismay all but 3 of the subjects got better - the world did not end then....Now just finished the number crunching on a second plantar fasciitis RCT. One group got the comfort model of Formthotics (not the regular one most use) and the other group got the same, but they were modified depending on the presence of risk factors for plantar fasciitis according to a strict protocol (ie tight calf muscles (lunge <38> heel raise; high force to establish windlass --> lateral column elevation; etc) --- we would have thought that this time we would find some differences .... but no - there was no difference between the two groups and everyone showed some symptomatic improvement ..... now you can see why I am in a "mood".At the end of the day, I just now think that when it comes to clinical trials with foot orthoses, that the placebo effect and Hawthorne effects are so powerful, everyone seems to get better .... this is forcing me to have a major rethink about how we really should be designing our foot orthoses clinical trials.

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