It's sort of funny (though also sad) that the knee is hurting while playing soccer from playing with the girls, and not hurting from playing soccer while playing with the girls. Old age is a bitch.
Old age can also make people wiser. In this case, if the knee truly no longer hurts from playing soccer, that fact can be seen as evidence of such acquired wisdom.
I wish I had signs of wisdom in my knees, like Peter apparently does...