Penisknee is a photographic optical illusion wherein a photograph's subject appears to have a penis that extends the length of the thigh to the knee. It is a result of a combination of shadows and the contours of the subject's clothing. Penisknee is rare and when properly seen the viewer can experience a Gestalt Switch between perceiving the illusion of the penis and the knee that is actually being viewed.
The light and shadows on your knee are causing penisknee.
by Jaynan January 31, 2011