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Patients with knee osteoarthritis should have mild exercise every day to reduce inflammation, should walk with shorter steps to reduce knee loading, and should strengthen their upper leg muscles, to judge from new research. But studies have yet to say how much exercise is best, how often, and at what intensity.
Studies presented at the World Congress on Osteoarthritis 2013 added some useful new details to the solid existing evidence that modest exercise can reduce pain for osteoarthritis (OA) of the knee. Randomized trials have already established several of these benefits, as enumerated by Paul Messier PhD at the annual congress of the Osteoarthritis Research Society International:
• Adding exercise to weight loss improves pain, mobility, and physical function better than either alone, according to results of the randomized ADAPT trial that studied them separately and together among 360 overweight and obese patients over the age of 60.
• Exercise does not prevent loss of lean body mass in OA patients, but it also does not interfere with adherence to weight-loss diets. Results from this study also produced the well-known adage that every pound of weight lost reduces load on the knee by 4 lb.
Among the advances from new research presented at the meeting:
• Improvements in upper leg (quadricep and hamstring) strength and self-reported knee stability (but not in proprioception or range of motion) yield reductions in pain and gains in activity as measured by the WOMAC scale. This information comes from a randomized controlled trial at the Amsterdam Rehabilitation Research Institute that compared two 12-week exercise programs, one of which focused on knee stability.
• Moderate exercise probably needs to be repeated every day in order to reduce inflammation. This was the bottom line from a study involving measurements of the proinflammatory molecule NFkappaB in transgenic mice injected with lipopolysaccharide to trigger inflammation. Mice exercised on a treadmill either before injection, after, or both, showed significant down-regulation of the proinflammatory molecule (compared to mice left undisturbed), but the suppression lasted for only about 24 hours. "Most patients are asked to exercise two or three times a week," remarked Derrick Knapik, a medical student at the Ohio State University Medical Center who presented the results. "You really need daily exercise to suppress inflammation."
• Walking more slowly, with a short stride that will reduce knee flexion, may lighten the load on the knee. This insight comes from biomechanical gait-analysis studies by Messier and others using the customary force plate and video motion capture systems to assess subjects from the Intensive Diet and Exercise for Arthritis (IDEA) trial. Besides height, weight, and BMI, the factors that correlated most strongly with knee compression and knee shear were stride length and knee flexion (which correlate with each other), and velocity.
However Messier, who is head of the biomechanics program at Wake Forest University, declined to speculate about a general mechanism for the pain-relief benefits of exercise. There is as yet no general consensus about the intensity, frequency, or type of exercises that are both safe and beneficial in osteoarthritis, said May Arna Risberg PhD, associate professor at the Norwegian Research Center for Active Rehabilitation.