Jane with bad back at the doctor's place

Jane went to her doctor complaining of a bad back. After trying every
remedy that he knew, her doctor finally said, "Tell me, Jane, how do
you have sex?"
"I always have it doggy fashion", she said.
"Ah, that's it!" said the doctor. "Why don't you try having it on you back?"
"Have you ever smelled a labrador's breath?" said Jane.