Elsevier

The Knee

Volume 19, Issue 3, June 2012, Pages 163-175
The Knee

Review
Effect of footwear on the external knee adduction moment — A systematic review

https://doi.org/10.1016/j.knee.2011.05.013Get rights and content

Abstract

Context

Footwear modifications have been investigated as conservative interventions to decrease peak external knee adduction moment (EKAM) and pain associated with knee osteoarthritis (OA).

Objective

To evaluate the literature on the effect of different footwear and orthotics on the peak EKAM during walking and/or running.

Methods

A systematic search of databases resulted in 348 articles of which 33 studies were included.

Results

Seventeen studies included healthy individuals and 19 studies included subjects with medial knee OA. Quality assessment (modified Downs and Black quality index) showed an (average ± SD) of 73.1 ± 10.1%. The most commonly used orthotic was the lateral wedge, with three studies on the medial wedge. Lateral wedging was associated with decreased peak EKAM in healthy participants and participants with medial knee OA while there is evidence for increased peak EKAM with the use of medial wedges. Modern footwear (subjects' own shoe, “stability” and “mobility” shoes, clogs) were likely to increase the EKAM compared to barefoot walking in individuals with medial knee OA. Walking in innovative shoes (“variable stiffness”) decreased the EKAM compared to control shoes. Similarly, shoes with higher heels, sneakers and dress shoes increased EKAM in healthy individuals compared to barefoot walking.

Conclusions

Further development may be needed toward optimal footwear for patients with medial knee OA with the aim of obtaining similar knee moments to barefoot walking.

Introduction

Osteoarthritis (OA) of the knee is one of the most common rheumatic diseases with an estimated 12% of the American population over the age of 60 years being affected [1]. It is commonly associated with substantial pain and immobility [1]. More recently, the lifetime risk of symptomatic knee OA has been found to be nearly 1 in 2 overall, more than 1 in 2 for those with a history of a knee injury, and nearly 2 in 3 for obese people [2].

It is widely accepted that biomechanical forces are associated with the pathogenesis of OA [3], [4], [5]. In healthy subjects, the peak medial knee compartment load during early stance of walking is 2.3–2.6 times the bodyweight (BW) [6], [7], [8], [9], while the lateral compartment is subjected to a peak load of 1.7 times BW [9]. The higher bone mineral density of the subchondral bone of the proximal medial tibia compared to the lateral side supports the difference in mechanical stress between both knee compartments [10]. These findings may explain the higher prevalence of medial knee OA, which is estimated to be 10 times more frequent than lateral knee OA [11].

Since direct measurement of knee joint load is invasive, gait analysis has been used as an indirect method to quantify forces acting upon the lower extremity. The external knee adduction moment (EKAM) is a valid and reliable representative of the medial-to-lateral knee load distribution [7], [12]. This varus torque shows a typical pattern of a higher first peak and a lower and less distinct second peak during early and late stance, respectively, in both healthy and symptomatic subjects [13], [14]. There is evidence showing that patients with medial knee OA have a significantly higher first peak EKAM compared to a healthy population [14], [15], [16], [17], [18], [19], [20], [21], [22].

The EKAM during walking has been linked to the symptoms, initiation and progression of knee OA [23], [24], [25], [26]. Consequently, the first peak EKAM has become an important variable in research to determine the risk and progression of medial knee OA, and to evaluate the effects of interventions, such as surgery, in the management of patients with this disorder. Further, other lesions of the lower limb, such as an anterior cruciate ligament (ACL) or meniscal injury have also been associated with increased peak EKAM during walking [27], [28]. As these injuries form a high risk for the development of future knee OA, [5], [29], [30] it may be important that rehabilitative strategies are implemented with the goal of decreasing EKAM during activity.

Over the past two decades, modified footwear has been investigated as potential conservative management of knee OA. More specifically, lateral wedging has been used with the goal of reducing symptoms associated with medial knee OA, hypothetically by reducing the peak EKAM in these patients [4]. If specific footwear interventions are associated with decreased EKAM during walking and other physical activity, these may be useful toward the management of symptoms of patients with medial knee OA, and potentially to reduce the risk of future OA in people who are at increased risk, such as those with knee injuries. This review aims to evaluate the current knowledge on various footwear interventions in relation to the peak EKAM in healthy and subjects with disorders of the knee.

Section snippets

Search strategy

An electronic search was undertaken without language restriction of Medline, PubMed, AMED, CINAHL, EMBASE and Scopus databases from their original available dates to January 2011. The search strategy included a combination of keywords for inclusion and exclusion factors (Appendix A). These were followed by hand searches relevant journals. Finally, the citation lists of included studies were screened for additional relevant articles via the database Web of Science.

Inclusion criteria

  • i.

    Peer-reviewed and published

Database search

The full search yielded 348 articles (Fig. 1). After exclusion of duplicates, irrelevant titles and screening of abstracts 39 remained. Six articles were excluded after full assessment as they did not use knee joint moments as an outcome measurement, used a biomechanical model instead of common footwear or were not published in peer-reviewed journals. Thus, 33 articles qualified for this review.

Risk of bias

The mean quality score ± SD of the included studies was 73.1 ± 10.6% (Appendix B). Fifteen of the studies

Discussion

This review investigated the effect of various footwear types on the EKAM in healthy and symptomatic subjects. Main subgroups were found for studies comparing wedges to a non-wedged or no insole, and studies comparing shod to barefoot walking. With the exception of two studies, all those that included subjects with medial knee OA using lateral wedges in a shoe reported significant reductions in the first peak EKAM, with a mean reduction ranging between 2.1 and 11.9%. A 5° lateral wedge was the

Conclusion

This systematic review provides evidence for immediate effects of footwear on the EKAM. There is evidence that: (i) the lateral wedge decreases the first peak EKAM during walking and (ii) shod conditions increase the first peak EKAM compared to barefoot walking and running. The orthotic is effective as a load-reducing intervention for patients with medial knee OA, while normal walking shoes were shown to be unfavorable compared to barefoot. In healthy subjects modern footwear increased EKAM

Conflict of interest

There is no conflict of interest.

Funding

No funding has been received for this study.

Acknowledgment

We wish to thank Professor Peter Herbison (Department of Preventive and Social Medicine, University of Otago) for his assistance with the analysis of this review.

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