At what age should your knees start aching?

[TERFCat]

I'm in my 30s and my knees/ upper thighs have started aching after mid/long walks. It's not painful, just tiring.

Is this just part of growing older, or might it be something else?

I also seem to have plantar fasciitis if it could be related?

it may be stemming from your plantar fasciitis.
have you got good shoes?
are you walking on hard ground?

I'm 53. My knees don't ache at all. I would think its not inevitable and its probably something else you have going on.

Are you overweight?

also no pain and i am 58