The answer to your question should come from the client’s physician, surgeon, and/or physical therapist. In general, hip replacement leg should not cross the middle to the opposite side. Excessive ROM is also avoided for the hip. The knee in general should avoid lock out and hyperextension. Knee flexion is generally hoped to achieve 110 degrees. More than this is not necessary for almost all knee replacement clients.
For the most part exercise can include quite a variety. Again the medical team is the place to start for recommendations. I have had a few clients determined to run and play tennis with knee replacements. Which is not a good idea in my opinion. Water exercise is excellent, once the surgical wounds have healed. Without any medical recommendations, I really wouldn’t advise beginning a program with such a client.