I've always thought the recumbent exercise bikes were easier on the back and I have lower back pain from arthritis. I had a combination recumbent bike and elliptical combination (Proform Hybrid Trainer) - The one I had was an older and less expensive version of the current one here - https://www.proform.com/hybrid-trainers/hybridtrainer. Last summer I replaced it with a Teeter FreeStep Cross Trainer to get a more natural like walking up and down motion with my legs and also better to help with upper body strength which I need - https://teeter.com/product/freestep-lt1/.

All of the before and after exercises were specifically to help with the rehab of the knee after the surgery - the stronger the leg and muscles/tendons around the knee, the easier it will be to get back to normal after the surgery. I don't think it would have helped to avoid having the surgery.

@rorygrabowsky My TKR had to be delayed for a few years due to platelet problems. During that time I exercised my knee a lot and got to the point where I had much less pain. A number of people did not understand why I still went through with the TKR but I figured that eventually I would need it and the current thought seems to be not to wait until you can't manage without, but to get it when you know do need it. If you wait until you are in very severe pain the rehab is more difficult. That being said, I do not have the flex I would like to have, and for me as with most people, replacement knees are not as good as natural knees, so I am not sure if I jumped the gun or not.

I think it's really a personal choice and if you manage to get your pain under control I think delaying the TKR may not be a bad idea, unless your orthopedic doctor has reasons that would contradict that. My doctor is pretty honest so I would trust his opinion. There are doctors, I am sure, who would want to get it done and not be as honest about waiting.
JK