This post contains adult material. Proceed when you are of legal age in your country.
Venus and/or Mars can represent sex and what turns us on. Capricorn represents control, discipline and the knees.
I have been hypothesizing that Venus/Mars in Capricorn may translate into a knee fetish. But based on informal surveys and rational thinking on the erogenous zone of the human body, it seems highly unlikely for there to be a knee fetish. Imagine my delight when I saw the photo below!