Exercise bikes after joint replacements (TKR and THR)

I am 57 years old and I had both hips replaced 3 years ago with anterior revision with cement ball. I am slim, and didn't realize I had received cement vs titanium until I asked for the operative report and noticed that, but it looked like my awesome surgeon (he's one of the best in the country) was trying different sizes until he found the correct one which is why he may I'm thinking have opted for the cement in the end, because both sides were tricky in that they were very long, almost 4 hour surgeries, due to a lot of mostly damage from torn labriums, and potholes in bone, and blood clots, etc. Anyhow I've been doing well, but just strained my back badly and my hips have bursitis now from what I'm told after a check. I had bursitis before surgeries as well. I don't know what exercise is best and feel afraid to try anything and have my first PT appointment on Monday. Does anyone know about the choices the surgeon makes for concrete vs titanium and why and also if it might make bursitis worse and what exercise I should do that would be best? thank you.

Reply to Judy, My start was foot rocking on recumbent bike, post 6wks now rocking on spinbike extremely close to a full pedal stroke. No stepper was suggested by physio, plus l could only stand idle for short time frames until my leg became fatigue, pain heighten. Plus still recovering from THR. Another question sent my way, Our local Hydro pool is 20mtrs x 10mtrs, yes you can jog in it. I'm not @ this stage of recovering. Keep healing everyone!