Knee surgery is a massive undertaking and does not have a great success rate as you get older. I've had three friends do it and they are still wobbling. I agree with everyone who has suggested the diet route. Carbs and sugar are the enemy of good health. Magnesium is your friend but not the shitty stuff. Vit D (I know it's sunny) but look up the work of Dr. Eric Berg. And exercise.
We are fine. We have money and one pension and no desire to love a Western expensive life. I travelled and lived in London for 23 years so I lived the life I wanted. I think if you have 2500 aud a month it's doable and that includes in hospital insurance
Greta, we are both struggling with living in Australia. We are not like some of the wealthy expats and we're middle aged (a bit beyond...) but we are trying to get DTV. It's a risk like anything in life however Australia is just going to get more expensive. We do not aspire to have a replicated Western life which would be expensive. You could teach English as a second language perhaps.