A woman complained to her doctor about bad knee pain.
After his tests showed nothing, the doctor asked, "Is there something you're doing that you haven't told me? Is there anything that might abuse your knees?"
"Well," she said sheepishly, "my husband and I do have sex doggy-style on the floor most nights."
"That must be it," said the doctor. "You know, there are plenty of other ways to have sex."
She replied, "Not if you're gonna watch TV, there ain't!"