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Does an Unloader Brace Reduce Knee Loading in Normally Aligned Knees?

  • Basic Research
  • Published:
Clinical Orthopaedics and Related Research®

Abstract

Background

Unloading knee braces often are used after tibiofemoral articular cartilage repair. However, the experimental basis for their use in patients with normal tibiofemoral alignment such as those undergoing cartilage repair is lacking.

Questions/purposes

The purpose of this study was to investigate the effect of varus and valgus adjustments to one commercially available unloader knee brace on tibiofemoral joint loading and knee muscle activation in populations with normal knee alignment.

Methods

The gait of 20 healthy participants (mean age 28.3 years; body mass index 22.9 kg/m2) was analyzed with varus and valgus knee brace conditions and without a brace. Spatiotemporal variables were calculated as were knee adduction moments and muscle activation during stance. A directed cocontraction ratio was also calculated to investigate the relative change in the activation of muscles with medial (versus lateral) moment arms about the knee. Group differences were investigated using analysis of variance. The numbers available would have provided 85% power to detect a 0.05 increase or decrease in the knee adduction moment (Nm/kg*m) in the braced condition compared with the no brace condition.

Results

With the numbers available, there were no differences between the braced and nonbraced conditions in kinetic or muscle activity parameters. Both varus (directed cocontraction ratio 0.29, SD 0.21, effect size 0.95, p = 0.315) and valgus (directed cocontraction ratio 0.28, SD 0.24, effect size 0.93, p = 0.315) bracing conditions increased the relative activation of muscles with lateral moment arms compared with no brace (directed cocontraction ratio 0.49, SD 0.21).

Conclusions

Results revealed inconsistencies in knee kinetics and muscle activation strategies after varus and valgus bracing conditions. Although in this pilot study the results were not statistically significant, the magnitudes of the observed effect sizes were moderate to large and represent suitable pilot data for future work. Varus bracing increased knee adduction moments as expected; however, they produced a more laterally directed muscular activation profile. Valgus bracing produced a more laterally directed muscular activation profile; however, it increased knee adduction moments.

Clinical Relevance

When evaluating changes in knee kinetics and muscle activation together, this study demonstrated conflicting outcomes and questions the efficacy for the use of unloader bracing for people with normally aligned knees such as those after articular cartilage repair.

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Acknowledgments

We thank Mr James Dunne and Mr Denny Wells for their assistance in data processing. We also thank Winthrop Professor David J. Wood for his assistance in the appropriate selection and stratification of healthy subjects to fulfill the study inclusion criteria and Drs Ben Jackson and Anne Smith for statistical assistance.

Author information

Authors and Affiliations

  1. School of Sport Science, Exercise and Health, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, WA, 6009, Western Australia

    Jay R. Ebert PhD, Timothy R. Ackland PhD & Cyril J. Donnelly PhD

  2. School of Sport and Exercise Sciences, University of Kent, Kent, UK

    Karen Hambly PhD

  3. Hollywood Functional Rehabilitation Clinic, Nedlands, Perth, WA, Australia

    Brendan Joss PhD

Authors
  1. Jay R. Ebert PhD
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  2. Karen Hambly PhD
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  3. Brendan Joss PhD
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  4. Timothy R. Ackland PhD
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  5. Cyril J. Donnelly PhD
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Corresponding author

Correspondence to Jay R. Ebert PhD.

Additional information

Funding provided by the Hollywood Private Hospital Research Foundation (JRE, TRA) and the National Health and Medical Research Council (JRE).

All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.

Clinical Orthopaedics and Related Research neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA-approval status, of any drug or device prior to clinical use.

Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.

This work was performed at the School of Sport Science, Exercise and Health, University of Western Australia, Crawley, Perth, Western Australia.

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Ebert, J.R., Hambly, K., Joss, B. et al. Does an Unloader Brace Reduce Knee Loading in Normally Aligned Knees?. Clin Orthop Relat Res 472, 915–922 (2014). https://doi.org/10.1007/s11999-013-3297-8

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  • DOI: https://doi.org/10.1007/s11999-013-3297-8

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