A woman goes to her doctor for a regular checkup.
"Well, Mrs. Smith, you appear to be in excellent health, your cholesterol is low, your blood pressure excellent, everything appears to be fine, but I'm actually quite concerned about those abrasions on your elbows and knees. How do they happen?"
She blushes for a moment and replies
"Well, they're from having sex, doggy style."
"Come now, you and your husband must know plenty of other positions?"
She thinks for a second.
"Oh we do, but the Doberman doesn't."