Look, I've just had a total knee replacement 7 weeks ago and I feel for what you are going through. All I can say is that my life was becoming pretty unpleasant because of my old knee and I really had to do something about it. Now understand if you have the operation your life won't get any better quickly, it has taken me the best part of six weeks before I started to feel better about things and it would probably be the same for you but it will get better. The operation is a piece of cake for modern surgeons, it's the rehab that takes the time and effort. That's the easy part, I know you have other issues re cost etc. All I can say is that you really have a clear decision. If your life is becoming miserable with pain and discomfort you owe it to yourself and your family to do something about it ASAP. Life is not about pain and misery, especially as we get older. From what you have said it seems that with a bit of financial sacrifice you can probably make it happen, if you can then do it. What is retirement worth if it is lived in pain and immobility?
I just wanted to say that you have had some really good and thoughtful responses and you had had some garbage posted as well. Forget about the overseas nonsense. Have a look at the lifestyle in some of these Asian countries. Do you really want to go there and let them cut you open? And let your post be a warning to others, going into retirement and older age without comprehensive private health cover is a very bad thing. People should not place themselves at the mercy of the public health system if they can help it, it's a tough lesson to learn and you have probably learnt the hard way.
Good luck whatever you decide to do and I hope things turn out well for you.