the knob

A woman visited a plastic surgeon who told her about a new procedure called 'The Knob,' where a small knob is placed at the top of the woman's head and could be turned to tighten up her skin and produce the effect of a brand new face-lift. Of course, the woman wanted 'The Knob.'
Over the course of the years, the woman tightened the knob, and the effects were wonderful, the woman remained young looking and vibrant.
After fifteen years, the woman returned to the surgeon with two problems.
All these years, everything has been working just fine. I've had to turn the knob many times and I've always loved the results. But now I've developed two annoying problems: First, I have these terrible bags under my eyes and the knob won't get rid of them.'
The doctor looked at her closely and said, 'Those aren't bags, those are your breasts.'
She said, 'Well, I guess there's no point in asking about the goatee.'