Kenneth McLeod, Sara Morley, Andrew Matsushima
J. Biomedical Science and Engineering, 2012, 5, 194-201 JBiSE
doi:10.4236/jbise.2012.54025 Published Online April 2012 (http://www.SciRP.org/journal/jbise/)

Muscle imbalances are a well accepted cause of mus-culo-skeletal pain, yet clinicians lack a simple, non- invasive, and reproducible means to assess muscle effort during activities of daily living. To address this issue, we have been developing vibromyography (VMG) as a means to quantitatively assess muscle mechanical effort such that accurate muscle effort ratios can be determined in the clinic. In this study, VMG was used to characterize muscle imbalances in older adults with low-level knee pain while they per-formed step-up and step-down activities. In addition to determining whether VMG can identify the im-balances previously reported in individuals with knee pain, we address the question of whether these knee muscle imbalances were a likely cause of knee pain, or whether the imbalances represented a coping re-sponse for pre-existing knee pain. A population (N = 30) of 35 - 85 year old men and women with a total of 42 painful knees were assessed. Robust multiple step- wise regression analysis identified weak hip abductor muscle effort relative to hamstring muscle effort as the best predictor of knee pain (p = 0.00006), with weak vastus lateralis effort in eccentric contraction, relative to concentric contraction, being the second best predictor (p = 0.0003). Muscle imbalances were able to account for 40% of the variation in reported pain, and the observed pattern of increasing knee pain with increasing quadriceps strength during con-centric contraction leads us to infer that the observed muscle imbalances are not the result of a protective action by the individual, but rather are a principle cause of the knee pain.

Keywords: Vibromyography; Knee Pain; Muscle Balance; Osteoarthritis

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