Centre Ave, Shadyside.
A man has bent over because of pain in his knee:

Old Lady: Are you ok?
Guy: Just fine. Something’s wrong with my knee, thanks.
Old Lady: You should exercise.
Guy: [smiling] I do.
Old Lady: You should lose weight. If you lose weight you put less weight on your knees.
Guy: My BMI is 21.
Old Lady: What’s a BMI?
[Guy awkwardly steps away.]

— Overheard by N.