Are external knee load and EMG measures accurate indicators of internal knee contact forces during gait?

Authors

  • Andrew J. Meyer,

    1. Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida
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  • Darryl D. D'Lima,

    1. Shiley Center for Orthopaedic Research and Education at Scripps Clinic, La Jolla, California
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  • Thor F. Besier,

    1. Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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  • David G. Lloyd,

    1. Griffith Health Institute, Griffith University, Queensland, Australia
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  • Clifford W. Colwell Jr.,

    1. Shiley Center for Orthopaedic Research and Education at Scripps Clinic, La Jolla, California
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  • Benjamin J. Fregly

    Corresponding author
    1. Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida
    2. Department of Biomedical Engineering, University of Florida, Gainesville, Florida
    3. Department of Orthopaedics and Rehabilitation, University of Florida, Gainesville, Florida
    • Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida. T: 352-392-8157; F: 352-392-7303
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Abstract

Mechanical loading is believed to be a critical factor in the development and treatment of knee osteoarthritis. However, the contact forces to which the knee articular surfaces are subjected during daily activities cannot be measured clinically. Thus, the ability to predict internal knee contact forces accurately using external measures (i.e., external knee loads and muscle electromyographic [EMG] signals) would be clinically valuable. We quantified how well external knee load and EMG measures predict internal knee contact forces during gait. A single subject with a force-measuring tibial prosthesis and post-operative valgus alignment performed four gait patterns (normal, medial thrust, walking pole, and trunk sway) to induce a wide range of external and internal knee joint loads. Linear regression analyses were performed to assess how much of the variability in internal contact forces was accounted for by variability in the external measures. Though the different gait patterns successfully induced significant changes in the external and internal quantities, changes in external measures were generally weak indicators of changes in total, medial, and lateral contact force. Our results suggest that when total contact force may be changing, caution should be exercised when inferring changes in knee contact forces based on observed changes in external knee load and EMG measures. Advances in musculoskeletal modeling methods may be needed for accurate estimation of in vivo knee contact forces. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 921–929, 2013

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