I had this problem with Harmony. Her hair is almost floor length. She would look so nice and clean except for her back legs. She seemed to be peeing on them, although I can't figure out how. So her legs would be all sticky and smelly just two days after bathing her.
I just couldn't stand it. So I shaved the inside of her legs down to the ankle. We haven't had a problem since and she now looks and smells great all over and you can't tell I shaved her legs unless she is laying on her back.
