There are some who suffer from degenerative joint diseases such as arthritis, and in some cases they don’t necessarily want to exercise, because quite frankly it can be more painful.  It can be harder to exercise, and in some ways it is logical to think that it might actually make your joint pain and joint degeneration worse over time, making it worse for you in the future, especially when you have a knee replacement or something else like that.  But the truth is that if you don’t exercise, you will suffer more.  You have to strengthen the muscles around those joints that happen to be hurting, and this will help to slowly relieve the pain over time.  The best way to go is to just exercise in ways that will be more sensitive to those particular joints that happen to be replaced, in pain, etc and take a good joint supplement using ingredients such as chondroitin and glucosamine as well as anti inflammatories to relieve the pain in general right now.  It’s a thing of use it or lose it.  The extra weight you will gain by not exercising will actually put extra strain on the joints, and otherwise you will not see a pretty picture as a whole.