I am soon to be 65 (female) and I work in retail--standing anywhere from five to eight hours a day--have for nineteen years. Anyway, behind my right knee, I have a lot of pain--going from the back of the knee down my calf. If I sit for a little while, when I go to stand up, I have to wait a few seconds before I can walk. When I am sitting, I have to put my leg in certain positions or I get a lot of pain from my knee down my calf. I have not been to a doctor as of yet. Do you have any idea what may be causing my pain?