Recently while out for a run, I came to a wide intersection where the Don’t Walk light was flashing. An older couple on the other side was waiting, and they glared at me when I sprinted across just before the signal changed. The husband snarled, “You runners think you’re so cool. Just wait til your knees go bad at 60.”

I soldiered on, assuming the guy must have been having a bad day. But I do know former runners who had to give it up because of bad knees.

Would it be better if I stopped running to prevent wear and tear on my joints? I called my friend I.P. Aard, a medical researcher at the National Institute of Running Sciences. I told her about the guy at the intersection.

“Buttercup, this is the second time in a week you’ve called me.”

“I know, but I have an important question. By the way, do you know that you are a very, very, pleasant woman.”

“Thank-you, sweet pea. It’s such a pleasure talking to you. So, the guy at the corner — did you tell him to mind his own business?”

“I should’ve. I just ignored him.”

“Good job—gold star for you. It’s true though that many runners have knee problems as they get older. If I were you, I’d be pricing wheelchairs right now.”

“No!” I shouted, hanging up. What a total downer. My day was ruined. The phone rang. It was I.P. again.

“C’mon, sugar plum, I was joking. You’ll be all right. Sure, some runners have knee issues, but you take care of yourself, you eat well, you don’t overdo it. Plus, the benefits of running far, far outweigh being sedentary.”

“That’s good news, I.P. I was really scared for a moment. Really scared.”

“There, there, Jim. It’s all right. Everything will be okay.”