A common question I hear is regarding how much exercise is safe to do if you have arthritis or want to prevent arthritis. A recent study suggests that both excessive exercise and a sedentary lifestyle may lead to early negative cartilage changes on MRI in individuals between the ages of 45-60. This is controversial. Prior X-ray studies have suggested that amongst certain extreme long distance runners, osteoarthritis is less common.
So how can we interpret the conflicting evidence? Well we know that regular exercise can decrease knee pain. This is likely due to beneficial biomechanical effects of muscle strengthening, and also due to benefits on a biochemical level as well. We also realize that people differ in exercise tolerance and ability. At a minimum we should all be exercising for 1 hour 3-4 times per week. If you’re able to exercise more and harder than that without significant pain, then pushing yourself is likely a good thing. If you have difficulty exercising more, then you should explore whether you have a medical condition limiting your ability. If you have a musculoskeletal condition that is holding you back, check to see if you have a biomechanical issue that can be improved with therapy, or a joint or tendon injury that can be improved with a focused medical therapy. Until there is more definitive evidence that a certain amount of exercise is bad for everyone, I don’t think we can specifically define our limits. Common sense, understanding what state of the art medical treatments can reasonably provide, and listening to your own body should keep you safe.