Therapeutic exercise relieves pain and does not harm knee cartilage nor trigger inflammation . Bricca et al BMJ People with knee OA must be reassured that therapeutic exercise prescribed to prevent or treat symptomatic knee OA is safe for articular cartilage and if anything, possibly improve cartilage composition. The belief that exercise is harmful for cartilage is based on misinformation. Instead of rest and activity avoidance, people with knee OA should be encouraged, reassured and supported to engage with exercise and physical activity, which is essential for good joint and general health. Exercise-evoked pain flares are to be expected when new to exercise but patients can be reassured that they diminish and usually disappears over the therapeutic exercise period.9 Furthermore, the benefits of physical activity and therapeutic exercise extend well beyond improvements in pain, function and quality of life in people with knee OA.10 Physical activity and exercise is vital to the prevention of at least 35 chronic diseases and beneficial in the treatment of 26, 9 many which are common in people with knee OA.