When you suffer from joint (especially knee) or back pain due to injury or arthritis, you enter into a vicious circle.  On the one hand, exercise will help you manage your weight and improve mobility but the pain makes it difficult to engage in any kind of exercise. One solution that has worked for some of my patients is exercise in water such as aqua aerobics.  Because you are not weight-bearing in water, the strain on your back and joints is greatly relieved but you still raise your pulse and improve your mobility.  Most leisure centres with a swimming pool have water aerobics sessions.  Even if you can’t get to a class, walking fast or jogging gently in water can help