Back in 2003, I went hiking on the Olympic Peninsula, on a trail that was very steep. The next day, my right knee seized up and it would not, could not bend at all. I went to see a doctor as soon as I could and ended up getting physical therapy for it. I think it was something like tendonitis maybe, beneath the patella.
In August, a group of us hiked a short section of the AT, and I couldn't walk down stairs for several days afterward. (Strangely, walking up stairs did not hurt.)
A couple weeks ago, we were out wandering the city for three hours, and my knee started to hurt. I actually forgot why; just thought I was wimpy. But lo and behold, it was two days before walking stairs normally.
Today I joined a fun photo walk with a couple folks, walking all of Broadway in Manhattan. I joined them at 125th at 3pm, and we made it to Times Square at 6pm. It was really fun and I think I got a few decent photos, but oh, my knee, it hurts really bad. Bad enough that I can't go up the stairs either, but have to do a sad little limp/hop instead.
I need a little footstool by my computer so I can play with the pics while I elevate and ice the knee. Being old and decrepit sucks.