degenerative osteoarthritis

I am suffering with degenerative osteoarthritis in my neck and lower bacik It is severe. I also have a hip that is in need of replacement that affects my back pain. I am unable to seek medical help at this time as finances unavailable. In the meantime, the thing I don't understand is this: if moving and exercise causes the bones to rub together, causing pain, how does exercise help?? does anyone know of any exercises that I can do that will help with the pain??