Foot posture (‘overpronation’) and the risk for overuse injury

I hate re-litigating an issue that I have written about so many times before (here, here, here, here, here, here and here) but here goes anyway: Early in my career, ‘overpronation’ was widely considered a problem, but by the late eighties I started to say that ‘overpronation’ was not a problem and since then have been widely preaching that and even wrote an opinion piece back in 1998: ‘Is Overpronation Really a Problem?‘ because that is what the evidence was starting to show. The research was mixed, some studies showing it was and some studies showing that it wasn’t a problem. Its not a matter of cherry picking the studies you want to believe to support what you want to believe (ie confirmation bias); at that time it appeared that the preponderance of the evidence was saying that it wasn’t a problem. When there is a sufficient body of literature on a topic, especially if there are mixed results, then it is time for the more formal systematic reviews and meta-analyses that pools all the data from all the studies. That was first done by Tong & Kong in 2013 (my review here) in which they concluded that ‘overpronation’ was a small but statictially significant risk factor for lower limb overuse injury. I had to change my mind, as that is what the preponderance of the evidence now showed. The Tong and Kong (2013) study included cross-sectional and prospective studies, now we had late last year, this new review that included only the more powerful prospective studies:

Foot posture as a risk factor for lower limb overuse injury: a systematic review and meta-analysis
Bradley S Neal, Ian B Griffiths, Geoffrey J Dowling, George S Murley, Shannon E Munteanu, Melinda M Franettovich Smith, Natalie J Collins and Christian J Barton
Journal of Foot and Ankle Research 2014, 7:55 doi:10.1186/s13047-014-0055-4
Static measures of foot posture are regularly used as part of a clinical examination to determine the need for foot level interventions. This is based on the premise that pronated and supinated foot postures may be risk factors for or associated with lower limb injury. This systematic review and meta-analysis investigates foot posture (measured statically) as a potential risk factor for lower limb overuse injuries.
A systematic search was performed using Medline, CINAHL, Embase, SportDiscus in April 2014, to identify prospective cohort studies that investigated foot posture and function as a risk factor for lower limb overuse injury. Eligible studies were classified based on the method of foot assessment: (i) static foot posture assessment; and/or (ii) dynamic foot function assessment. This review presents studies evaluating static foot posture. The methodological quality of included studies was evaluated by two independent reviewers, using an adapted version of the Epidemiological Appraisal Instrument (EAI). Where possible, effects were expressed as standardised mean differences (SMD) for continuous scaled data, and risk ratios (RR) for nominal scaled data. Meta-analysis was performed where injuries and outcomes were considered homogenous.
Twenty-one studies were included (total n = 6,228; EAI 0.8 to 1.7 out of 2.0). There was strong evidence that a pronated foot posture was a risk factor for medial tibial stress syndrome (MTSS) development and very limited evidence that a pronated foot posture was a risk factor for patellofemoral pain development, although associated effect sizes were small (0.28 to 0.33). No relationship was identified between a pronated foot posture and any other evaluated pathology (i.e. foot/ankle injury, bone stress reactions and non-specific lower limb overuse injury).
This systematic review identified strong and very limited evidence of small effect that a pronated foot posture is a risk factor for MTSS and patellofemoral pain respectively. Evaluation of static foot posture should be included in a multifactorial assessment for both MTSS and patellofemoral pain, although only as a part of the potential injury risk profile. Whilst the included measures are clinically applicable, further studies are required to determine their relationship with dynamic foot function.

The full text is at the above link, so I will not go over what they did except to say that it was a thorough good review and the results show what they show:

  • ‘Overpronation’ was a strong risk factor for medial tibial stress syndrome and a weak risk factor for patellofemoral pain syndrome
  • It was not a risk factor for other injuries.

This is consistent with the Tong and Kong review; ie ‘overpronation’ is a risk factor, but it is a small factor.

The only quibble I might have is the inclusion or exclusion of certain studies. For example, the Neilson et al (2013) study was included (my review of that study). An argument could be made that this study should not have been included due to the selection bias in the study (they excluded what were probably the high risk ‘overpronators’ and then found ‘overpronation’ was not a risk factor! … go figure!) and the criteria they used to determine ‘overpronation’ in their study means that many of the feet in their ‘neutral’ category would have been in the ‘overponated’ category in some of the other studies. This then raises questions about the criteria for what each study used to determine ‘overpronation’ and what feet make it into what category. A foot may be ‘overpronated’ in one study based on the criteria they used, but not ‘overpronated’ in another study based on the criteria that they used.

The authors did not include the Teyhen et al (2013) study (my review). This study found that a higher Foot Posture Index did increase the risk for injury. I do not know why this study was not included, but it was probably due to the nature of the publication (it was a full text conference presentation and not peer reviewed). I only mentioned this to make a point: Exclusion of the Neilson et al (2013) study and inclusion of the Teyhen et al (2013) study would have potentially changed the results on the above review in one direction. By modifying the inclusion and exclusion criteria for these types of reviews have the potential to bias the results one way or another. This is why the inclusion and exclusion criteria need to be explicitly stated.

Paradoxically, a few days after the above was published there was a blog post claiming that ‘overpronation’ was not the cause of overuse injury … go figure!. To support that claim, there was a quote taken from another blog post. The author of that other blog post even called them out for taking the quote out of context to twist its meaning. I see there has been no correction based on that ‘call out’. It also raises the issue of who you going to believe: A blog post that takes a quote out of context to change its meaning or a formal systematic review by experienced researchers that is published in a peer reviewed journal. I know who I would rather believe.

As another aside, there was this amusing spoof post in the satirical blog, The Spudd, not long after the above study was published, called “I just know” replaces systematic reviews at top of evidence pyramid” in which they lampooned those who ‘just know” they are right in the face of the preponderance of evidence:
The response to the above study in some social media circles and in the crankosphere blogosphere certainly reflects that model!

As always: I go where the evidence takes me until convinced otherwise …and this is what the evidence says. We have to be slaves to the data and not our preconceived biases.

Neal BS, Griffiths IB, Dowling GJ, Murley GS, Munteanu SE, Franettovich Smith MM, Collins NJ, & Barton CJ (2014). Foot posture as a risk factor for lower limb overuse injury: a systematic review and meta-analysis. Journal of foot and ankle research, 7 (1) PMID: 25558288

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3 Responses to Foot posture (‘overpronation’) and the risk for overuse injury

  1. blaise Dubois February 12, 2015 at 11:56 pm #

    Hi Craig,
    I deeply analyse the study… and I’have an extremely low confidence level in its results. Not because the study is not good, but because their results are very instable and because their analysis and conclusions suggest associations that doesn’t exists.

    See my critics :

    What is your level of confidence that foot pronation/posture is a risk factor for MTSS or PFPS?

    • Craig Payne February 15, 2015 at 10:50 pm #

      Its what the data shows. Its a weak but statistically significant link.

      I would rather not beleive it as it did not fit with my ‘model’ or understanding of MTSS, but the data shows what it shows. The data is consistent with a previous systematic review and meta-analysis and it is consistent with another review that included cross-sectional studies (the above one was only prospective) … the relationship is there, but it is a weak one (which makes sense as MTSS is multifactorial) … I now have to modify my ‘belief’ or ‘model’ of what I think MTSS is…

      As TX Huxley once said … “the great tragedy of science is that slaying of a beautiful hypothesis by an ugly fact”.

  2. blaise Dubois April 5, 2015 at 6:46 pm #

    Sorry Craig, but the conclusion of a specific data (even “level 1” evidence) is not always reflecting the reality of all the prospective studies… See discussions with Christian Barton on the comments section of the blog.

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