I've always had crappy knees. They used to only react to specific triggers -- airplane and theater seats, mostly (and that one time I wore a 30lb costume in dress shoes a size too small for over eight hours straight with nowhere to sit, but honestly, I can forgive them that one) -- and I could hide it from most everyone.
I will never forget my ex, on seeing that my knees weren't working, and that I asked for their arm to help control the worst of the limping, told me with condescension that "people like me" needed to give "real people" like them prior notice in writing of any assistance I might need so that they, the real people, could decide if what I was asking was "appropriate."
Two weeks to doc referral, and hopefully less to physio consult. It's all so dumb. Stupid knees, let me walk!