"Broken Leg" joke

"HOW DID IT HAPPEN?" the doctor asked the middle-aged
farmhand as he set the man's broken leg.
"Well, doc, 25 years ago..."
"Never mind the past. Tell me how you broke your leg this
morning."
"Like I was saying...25 years ago, when I first started
working on the farm, that night, right after I'd gone to bed, the
farmer's beautiful daughter came into my room. She asked me if
there was anything I wanted.
I said, "No, everything is fine."
"Are you sure?" she asked.
"I'm sure," I said.
"Isn't there anything I can do for you?" she wanted to
know. "I reckon not," I replied.
"Excuse me," said the doctor, "What does this story have to
do with your leg?"
"Well, this morning," the farmhand explained, "when it dawned
on me what she meant, I fell off the roof!"
Source: Steven Stuart-Doig,
Director, AISS Information Center, University of Illinois At Chicago