Although no consensus exists on the definition of “overpronation,” its consequences are well known,
In clinical practice, gait patterns and lower extremity alignment and kinematics are routinely assessed when clinicians are confronted with conditions ranging from local injuries to low back pain to general movement dysfunctions. Important components of a comprehensive evaluation are to observe the static and dynamic function of the medial arch of the foot. Although no consensus exists on the definition of ‘overpronation’, its consequences are well known, biomechanically logical, and supported by the literature. In conjunction with internal rotation of the tibia, valgus collapse at the knee and an increased adduction moment at the hip, overpronation can contribute to a myriad of biomechanical concerns and conditions such as stress fractures, Achilles tendinopathy, patellofemoral pain syndrome, plantar fasciitis and medial tibial stress syndrome, to name a few.
A variety of interventions are commonly employed to address overpronation, including pre-fabricated and custom foot orthotics, motion control footwear and taping. The two papers included in this review sought to synthesize the literature on the efficacy of these interventions on addressing overpronation1 and summarize the effects of foot orthotics on gait2.
Efficacy of Foot Orthoses, Motion Control Shoes & Taping for Controlling Overpronation
- Of the 29 studies included in this review (which included a total of only 429 subjects!), 13 evaluated foot orthotics, 10 looked at motion control foot wear and 10 at adhesive taping (some examined more than one intervention).
- Average PEDro scores were ~5.5/11 across the included studies.
- Overall, the reduction in calcaneal eversion (an indicator of pronation) for the three anti-pronation interventions was significant when compared with no-intervention control (p < 0.001). The reduction with therapeutic adhesive taping was the highest (mean difference = 2.64°; 95 per cent CI = 1.39 to 3.90), followed by the motion control footwear (mean difference = 2.52°; 95 per cent CI = 1.71 to 3.33), and lastly were foot orthoses (mean difference = 2.24°; 95 per cent CI = 1.42 to 3.07). It should be noted that the overall difference between the most effective and least effective interventions was less than 0.5°.
- Within the orthotic data presented above, custom made orthoses seemed to have a bigger effect on rearfoot eversion than prefabricated orthoses (2.35° vs. 2.08° on average; again, a small difference).
- Regarding the design of motion control footwear – the shoes with dual materials in the midsole produced a reduction in calcaneal eversion (mean change = 2.77°; 95 per cent CI = 1.74 to 3.81; p < 0.001). Conversely, the effects of motion control footwear with heel flare or wedge modification were not significant.
- Regarding taping techniques – Low-dye taping had a non-significant weighted mean change in the reduction of foot pronation (mean change = 1.50°; 95 per cent CI = −0.73 to 3.73; p = 0.19). Interestingly, other taping techniques, including high-dye and stirrups taping techniques, were found to be effective in controlling foot pronation (mean change = 4.62°; 95 per cent CI = 3.73 to 5.50; p < 0.001).
- Overall, all three interventions can potentially improve overpronation. Foot orthotics were the least effective means and therapeutic taping was most effective. However, remember the difference among the three interventions was only about 0.5°. The relevance of such a difference is questionable and it could result from measurement error and inconsistencies amongst the studies included.
Mechanisms of Action for Gait Alterations with Foot Orthotics
- Quality index scores of the 22 included studies ranged from 17-24 out of a possible score of 28.
- The most common shortcomings of the studies included lack of assessor and participant blinding, and generalizability of the samples.
- To date, research has focused primarily on the kinematic paradigm and least on the neuromotor control aspects of orthotic utilization.
- Kinematic paradigm: Pooled results demonstrated a relatively small effect on rearfoot eversion and tibial internal rotation (~2° each) – both were measured via skin markers and may therefore overestimate actual bone motion. Posted, non-moulded orthoses (moulding = customizing contour of orthotic to patient’s foot, +/- posting) seemed to have a greater effect. The clinical relevance of this small change is unknown, but the cumulative effect of smaller changes on overall mechanics and tissue strain should not be discounted. Wide confidence intervals in most studies suggest that responses may be very individual.
- Shock attenuation: Surprisingly, altering material density had no effect tibial acceleration, loading rate or vertical impact force. However, moulded orthoses may reduce loading rate and favorably affect vertical impact and ground reaction forces.
- Neuromotor control: Only two studies contained enough data to derive point estimates of effect, but pooling was not possible due to dissimilarity of the cohorts. Having said that, orthotics do seem to increase tibialis anterior and posterior activity (the myofascial ‘sling’ supports of the foot’s arch), as well as variably affect medial gastrocnemius activation and thigh muscle activity (contingent on injury status) – further research is required in this area.
- Overall this review concluded that there is wide variability in how individuals respond to orthotics. Posted orthotics that aren’t customized seem to affect rearfoot kinematics and tibial internal rotation, while moulded (customized) orthotics may attenuate loading rate and vertical impact force.
- Readers should keep in mind that most studies included subjects with no history of injury so further research is certainly required on a variety of patient populations.
CONCLUSIONS AND PRACTICAL APPLICATIONS
These two studies did a nice job of summarizing the existing literature on the effect of orthotics on gait mechanics and how external devices can influence pronation and other movement/force variables.
In general, it appears that orthotics, motion control footwear and taping are all potentially effective for reducing overpronation. Practically speaking, orthotics or footwear seem more reasonable despite the fact that taping was most effective when data was pooled. This difference was minimal, and taping is not a reasonable, long term solution in most cases. The literature also suggests that non-customized, posted orthotics may control rearfoot eversion and tibial motion more than a control intervention, while customized orthotics may have more of an effect on loading and force attenuation than if they are just posted (When was the last time an orthotic company rep gave you this information?).
Given that patient response to orthotics seems to be variable (this is something the literature demonstrated quite clearly), clinicians should continue to customize their prescription after careful assessment and evaluation of each patient.
Both studies conducted appropriate literature searches utilizing standard databases. Authors from each project then selected studies according to well described inclusion criteria that were appropriate for the topics at hand. Cheung and colleagues1 included randomized or quasi-randomized trials (n = 29) published in peer-reviewed journals that investigated the efficacy of foot orthotics, motion control shoes or taping versus no-intervention control groups for patients diagnosed with conditions related to excessive foot pronation (who were otherwise healthy). Mills and colleagues2 included only studies (n = 22) that focused on the mechanisms of effect for foot orthotics on gait (studies looking at the effects on running, jumping, single-leg squatting etc. were excluded). Studies evaluating the efficacy of orthotics were not included. Reporting on study selection and quality assessment was adequate in both papers.
Dr. Shawn Thistle is the founder and president of Research Review Service Inc., an online, subscription-based service designed to help busy practitioners to integrate current, relevant scientific evidence into their practice. Shawn graduated from CMCC and holds an Honours Degree in Kinesiology from McMaster University. He also holds a certificate in Contemporary Medical Acupuncture from McMaster University, and is a Certified Active Release Techniques (ART®) Provider. For more information about the Research Review Service, visit www.researchreviewservice.com .
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