“Need” in terms of arthroplasty to correct osteoarthritis is a broad gap, rather than a bright line. The point CP is making is that we generally don’t bother giving old people total knee replacements because it costs a ton of money and they won’t be around long enough to get full use out of them. They’re also at increased risk of death due to surgical complications, and so on. They may medically need one, but still not be good candidates.
You can see some representative figures discussed here, though.
Considering that, given the costs per-capita and as a percentage of GDP in other first world countries, one could reasonably estimate that an additional trillion dollars formerly spent on health care will become available for other uses in the economy. That’s enough to create 20 million new jobs at the national average annual income.
So even if 75% of that freed capital is sequestered in savings, offshore accounts, invested in financial boondoggles, or otherwise “wasted” we stand to be able to create an order of magnitude more jobs than will be potentially lost.