Muscle dysfunction and effective rehabilitation of knee osteoarthritis: What we know and what we need to find out

In knee OA, quadriceps sensorimotor dysfunction - weakness, impaired proprioceptive acuity, and impaired neuromuscular protective reflexes - is associated with pain and disability. Intuitively we usually assume that joint damage causes and precedes pain, resulting in reduced mobility and muscle weakness, but this assumption and may be incorrect because there is evidence that quadriceps dysfunction may play a role in the pathogenesis of knee OA. Exploiting muscle's fantastic physiologic plasticity, exercise provides us with powerful potential strategies to retard, prevent, and even reverse some of the pathologic processes in knee OA. If muscle dysfunction is involved in the pathogenesis of knee OA, then maintaining strong, well-conditioned muscles may prevent the onset of OA. For people with established OA, there is now convincing evidence that exercise improves muscle sensorimotor dysfunction and reduces pain and disability without exacerbating joint damage. We now need to develop and evaluate clinically effective exercise regimens that can be delivered to the large patient population in the community, and maximize the benefits of the regimen by identifying strategies that encourage and enable participation in regular physical activity. This will enable patients to appreciate the benefits of physical activity and actively participate in the self management of their condition.