Therapeutic exercise for knee osteoarthritis: considering factors that may influence outcome.

While exercise has been shown to be beneficial for reducing pain and improving physical function in individuals with knee osteoarthritis (OA), there are still individuals who do not always respond well to this treatment approach. There are a number of factors that have been shown to influence either the degree of disability and/or the progression of disease in individuals with knee OA. These factors include quadriceps inhibition or activation failure, obesity, passive knee laxity, knee alignment, fear of physical activity and self efficacy. It may be possible that varying levels of these factors might also interfere with an individual's ability to participate in an exercise or physical activity program or minimize the benefits that can be achieved by such programs. This paper examines the influence of these factors on physical function and their potential for altering the outcome of exercise therapy programs for individuals with knee OA. Implications and suggestions for potential adjunctive interventions to address these factors in future research and clinical practice are also discussed.