I have bad knees to the tune of a couple of knee operation, its really impacted my kicking ability. My right knee is the worst and oddly it has made my left foot kicks weak due to it not functioning well as a support.
As far as the age thing in general goes I didn't realize that I was old until I had the following exchange with one of my soldiers.
"Hey, Sergeant, when did you graduate high school?"
I replied, "1992".
"Wow, really? I was two"
Very painfull.
Mark
P.S. It hurt a lot worse when I realized that he had been born in 1990. That was the year I made Shodan.
My step daughter has a routine similar to that..I will tell a story from the years I traveled and she will ask " What year was that again?" I will tell her and her response is " I wasn't even born yet"...