THE EVIDENCE FOR EXERCISE
Biomechanical factors such as joint misalignment play a role in the development and progression of OA. Other risk factors, such as muscle weakness, impaired motor control, and diminished physical fitness, are modifiable with exercise. The evidence for the use of exercise in the management of symptomatic OA has evolved over the past two decades and includes clinical trials of several types of physical activities. Data from large randomized, controlled trials (RCTs) and systematic reviews of the literature indicate that exercise provides small to modest benefits (effect sizes ranging from 0.2 to 0.4) for pain relief, improved function, and reduced disability.10, 13-19 However, details on the frequency, intensity, duration, and type of exercise (aerobic, flexibility, dynamic or static strengthening, balance activities) are not always specified.20 Helmark and colleagues re- ported that in a group of women with knee OA, exercise increased both intra articular and per synovial concentrations of interleukin-10, an anti-inflammatory cytokine that protects chondrocytes (cartilage cells) and may be responsible for the benefits for OA seen with exercise.21