What I find annoying about doctors and being over 60

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1. There are also millions of people over 60 who do have knee problems and find ways to deal with it

and stay very active.

You're right, that doctor's attitude is infuriating and unacceptable. Not all doctors have that attitude. You need to find somebody else, quick. Going from no problem to sudden agony is not something to fool with, and there are doctors out there who won't brush it off. I actually think younger doctors might be more pro-active about it because they're used to thinking of fitness and exercise as a basic part of health. They know that a "bad knee" is a serious thing.

Good luck to you!