This is a "catch-22" situation. It is nearly impossible for most people to loose weight without exercising. Weight gain, in turn, can worsen arthritis pain in the lower body due to the added pressure on the knee joints. You need to find activities that you can tolerate. Walking is great for most, but not all, patients with knee arthritis. You might try water aerobics, bicycling, or yoga instead. You may also want to work with a physical therapist who can help you ease into an exercise program that is right for you.