I had my left knee replaced and I was released from the hospital next day. I am doing the physical therapy and it HURTS. I strap my leg into a machine a couple, three times a day and it manipulates my leg. I can control the amount of extension and flex . But you have to push the limits to get any benefit. The Doctor likes his patients to spend 6 hours a day on the machine. I have not worked up to that yet. Some folks sleep with their leg in the machine. I tired that the first night in the hospital and after 1 ½ hours I pushed the snivel whine button and had the staff take the thing out of my bed. I may try it tonight and see how well I do.