In 1997, I had bilateral (2) knee replacements due to osteoarthritis (bone-on-bone). Prior to the surgery, I had cortisone injections on both knees because I was planning to go on a trip and it would entail a lot of walking. After being pain free for a month, the pain returned. As far as I was concerned, the pain felt worse or, perhaps, it felt so good to be without pain. The effects of the cortisone injection lasted only for a month. It was after being without knee pain for a month and enjoying it so much, that I decided to have both knees replaced at the same time. It has been a long recovery period, but the surgery was well worth it.