In addition OA is the most common cause of inactivity among the elderly and many fear that activity will further damage the joints. Inactivity is a large risk factor for poor physical and psychological health as well as premature death. Level of physical activity in people with OA has mainly been evaluated by self-assessment questionnaires. People with hip OA are more active than people with knee OA and the correlation between the degree of radiographic changes and physical activity is weak. Only 30% with early OA of the knee in the age group 35-65 years meet the recommendations for physical activity performed at least 30 minutes per day of moderate intensity, five days per week, measured by an accelerometer.