A medical device opine by me.

I will cross post at my http://65y.com I don't want to "name names" here because I was given good answers when asked (after my internet research).
Basically three years ago I fell off a bicycle and had a very painful knee. I had/have Health Partners who referred me to a specialist. Judging from the office I lot of local sports figures have used this doctor so I figure that he is competent.
I had knee joint necrosis shown by X-Ray and MRI. This doctor correctly predicted that my tendon injuries would heal themselves with time and that things would go better if I lost weight. These are all true. He mentioned a three month waiting list for knee replacements and asked me if I want to get on the list.
I told him that I had two years before the option of early civil service retirement, which I took http://ruleof90.com so I hoped to "tough it out" until then. He wished me luck but advised me to lose weight and questioned weather my knee would hold out that long.
My "out of pocket" costs" were reasonable, I think $10 per visit and 10% or $100 for the MRI were reasonable. Again, this was Health Partners.
Three years later I have retired and have not had knee replacement surgery. The knee joint is maybe six or seven on mobility things that give me some trouble. The tendons are near the top of the list and they would probably be a lot worse with a knee replacement. Part of it is "first pain". Tonight I was working on a challenging home repair project where I was on my feet constantly for more than two hours. Initially, some joint pain but mostly minor muscle pain. Nothing serious.
Anyway, when I was in this doctor's office there was a woman from a nursing home who had to be over 80 and there was a transportation dilemma that I overheard. The woman's daughter arrived and she and the staff were discussing transport option back to the nursing home for her mother. I overheard the doctor explaining to the daughter how the woman was a candidate for a knee replacement.
The old woman barely recognized her daughter (my mother, until her death recognized me the moment I got near her, bless her, and hugged and kissed me enough to make girlfriends jealous but she was diagnosed with dementia)
The old woman in the doctors office had classic dementia/Alzheimer's symptoms and she was in nursing home but the doctor was setting her up for a hip replacement!
Before I retired I worked with a couple of people with hip replacements. You have a three month rehab time with hip replacements and that assumes you are motivated. That's on par with a knee replacement. I have a number of people at work who had had knee replacements or knew someone at work so I kept track of the rehabs. Typically three months and this is with motivation and aggressive rehab.
That said, if I decided on a knee-replacement I would trust this doctor to do it, but he seems to advise them like "popcorn". The rehab cost is huge after the surgery. I wondered how this 80 year old woman with Alzheimer's would handle rehab, which I considered very tough.
Again, I considered my out of pocket costs of under $200 to be reasonable and all my questions were answered well but I consider myself to be very informed.