Background Knee osteoarthritis (OA) is the most common chronic joint disease. Quadriceps is the muscle around the knee joint more affected by the disease, resulting in a reduction in functional muscle parameters. This may contribute to substantial functional deficits, however it is not clear if functional muscle parameters, like total muscle work, correlates to physical function in early degrees of knee osteoarthritis.
Objectives The aim of this study was to evaluate the correlation between functional impairment and knee extensor total muscle work in men with Grades I or II knee OA.
Methods Fourteen men with knee OA grade I or II (according to Kellgren & Lawrance criteria) participated in this study. The physical function section of the Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC) questionnaire was applied before the isokinetic evaluation. The concentric and eccentric knee extensor total muscle work were assessed using Biodex System 3 Pro isokinetic dynamometer, at a speed of 90°/s. Spearman's correlation coefficient was used to detect the relationship between the dependent variables (WOMAC questionnaire physical function section score) and the independent variables (average total muscle work). For all the statistical tests, the significance level was p<0.05.
Results The data analysis revealed a moderate and negative correlation between self-reported physical function and eccentric extensor total muscle work (r= -0.8, p=0,001). The self-reported physical function presented no correlation with concentric extensor total muscle work (r= -0.5, p=0,07).These results indicate that the higher the knee extensor eccentric total muscle work, the lower the level of functional impairment self-reported by these individuals.
Conclusions Our results indicate that correlation between eccentric knee extensor total muscle work and self-reported physical function are already present in individual with early degrees of knee OA. These results also indicate the lower the total work, the greater the functional deficit.Thus, physical therapy programs are indicated for these patients to improve physical function, especially in functional activities involving eccentric contraction of the quadriceps.
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Acknowledgements The Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP), São Paulo, Brazil for financial support (#2007/07200-4; #2011/06619-7).
Disclosure of Interest None declared