Risk of Injury From ‘Pronation’

“Overpronation” and “pronation” are by and large misunderstood and most discussions of it are based on the straw man fallacy and a superficial understanding of it. This means that those discussing “overpronation” and “pronation” are actually discussing something it is not, and then discussing or critiquing that false characterization. I have already done one rant on it: The nonsensical understanding of ‘overpronation’.

“Overpronation” and “pronation” have been linked to so many overuse injuries that can occur in runners, except the evidence for that link is either not existent or very weak. Almost all prospective studies on “overpronation” and “pronation” have found that it does not increase the risk for injury. Those who have listened to lectures I have given over the last 20 years know what I have been preaching exactly that. However, the weakness of many of those studies is how they measured “pronation”; for example, some measure calcaneal eversion; some measure navicular drop; some do a footprint analysis; and some use a dynamic 3D kinematic analysis. The problem with that is that someone may be ‘overpronated’ on the measurement of one parameter and not ‘overpronated’ on another parameter. A classic example is the measurement of navicular drop, which only measures the sagittal plane drop of the arch – it does not take into account all the other components that go into “overpronation”, such as calcaneal eversion, medial midfoot bulging and forefoot abduction. How much of each one of those you get will depend on the orientation of the various joint axes that motion occurs at in the foot, and we know from the data that there is substantial inter-individual differences in those orientations. So, to just use something like navciular drop to measure “overpronation” will miss the “overpronated” feet that have normal navicular drop, but a large amount of navicular drift in the transverse plane, but would still be considered “overpronated”.

So, even though the prospective studies are showing weak or no relationship between “overpronation” and risk for injury, how much weight should be given to those conclusions if what they were measuring was only one component of “overpronation”. This is one of the reasons that Tony Redmond developed the Foot Posture Index (FPI) to give a measurement of the posture of the foot based on all those components and address the shortcomings in some of the traditionally used measures. More and more studies are now appearing in which the FPI has been used.

Now we have a prospective study in a military population that used the FPI to determine risk (and the cost of injury) which shows that “overpronation” does increase the risk for injury:

Impact of Foot Type on Cost of Lower Extremity Injury
Deydre S. Teyhen, Lindsay A. Nelson, Shane L. Koppenhaver, Laura K. Honan, Alli E. McKay, Andrea R. Young, Douglas S. Christie
Source
Purpose/Hypothesis: Lower extremity musculoskeletal injury (MSI) affects over 720,000 service members annually. Ankle and foot injuries (including stress fractures) have accounted for approximately 40% of these injuries, and the most common complaint during an infantry road march under load was overuse related foot pain. Although risk factors for MSI are multifactorial, good evidence suggests that foot type serves as an intrinsic risk factor for lower extremity MSI. However, information related to the impact of foot type on the medical costs of lower extremity MSI in the military is limited. The primary purpose of this study was to determine the relationship between foot type and medical costs associated with lower extremity MSI. An additional purpose was to describe the utilization of healthcare and which lower extremity regions incurred these costs.
Subjects: One thousand healthy U.S. military healthcare beneficiaries were enrolled as part of a larger study. Of those, 668 participants (M = 392, F = 276; age 30.1 ± 7.4 years, BMI 25.8 ± 3.3 kg/m2) who continued in active military service for at least 18 of the following 31 months were included in this analysis.
Materials/Methods: Static foot posture was quantified using the Foot Posture Index (FPI-6). Medical costs, diagnostic codes, and relative value units (RVUs) associated with healthcare visits for lower extremity MSI over the subsequent 31 month period were acquired from the military healthcare database. Healthcare utilization was categorized according to body region (lumbopelvic, knee, leg, ankle, foot, and unspecified). Univariate ANOVA and Sidak post hoc analyses were performed to compare costs, regions of injury, and static foot posture.
Results: Three hundred and thirty six (50.3%) of 668 participants sought medical care for lower extremity MSI during the study period, totaling 2,112 medical visits and a cost of $436,965. Costs varied significantly by foot type for injuries below the knee (p < .05). Post hoc analysis demonstrated that the extreme pronated foot type resulted in increased RVUs for leg injuries (p=.02) and increased visits for injuries from the knee to the foot (p=.02), and in the leg region (p=.003) when compared to the normal foot type.
Conclusions: Pronated feet, as assessed by the FPI-6, were associated with significantly higher injury costs and healthcare utilization for injuries from the knee to the foot, especially in the leg and foot regions. Our findings are consistent with previous researchers who have found that extreme scores of the FPI-6 were associated with increased injury risk. Future research should determine if correctly identifying people with foot types susceptible to severe lower extremity MSI could help reduce future injuries and injury-related costs.

I can’t quite ascertain the nature of this publication. It turned by in my Google Scholar alerts and is available for download as a word document from the NATO website. I have searched for a proper citation but can not find it. This was a large prospective study. The methodology and the analysis looks fine and clearly (and strongly) showed that an “overpronated” foot increased the risk for injury.

This study that used a more valid measure of all the components that go into “overpronation” is telling me that there is increased risk for injury. In contrast many of the other studies that are telling me that there is no risk, yet only measured one component or parameter of what would be considered “overpronation”. I guess I will have to pull out what hair I have left to try resolve this one.

tearhairout

As always, I go where the evidence takes me until convinced otherwise, and you can’t cherry pick this study or some of the others to make the point that is trying to be made depending on your world view.

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One Response to Risk of Injury From ‘Pronation’

  1. Craig May 9, 2013 at 8:18 am #

    Finally have a proper citation for the above paper:

    Teyhen DS, Nelson LA, Koppenhaver SL, Honan LK, McKay AE, Young AR, Christie DS: Impact of foot type on cost of lower extremity injury. NATO Science and Technology Symposium, Milan, Italy, April 16, 2013

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