An elderly couple was sitting outdoors at a cafe when they noticed an old man who seemed to be having trouble crossing the street with an ungainly shuffle.
The man said to his wife, “He surely has bad arthritis to walk like that.”

His wife replied, “No, that’s definitely old-time rheumatism.”

They couldn’t agree so the man decided to ask the old man.
He walked over to him and said,
“Excuse me, sir, but my wife and I saw you having difficulty crossing the street and I told her that you have arthritis but she insisted that you have rheumatism.
Which one of us was wrong?”

The old man said, “The three of us were wrong.”
“Three of us were wrong? How so?” asked the man.

To which the old man replied,
“You were wrong when you said I had arthritis, your wife was wrong when she said I had rheumatism, and I was wrong when I thought I just had to pass gas.”