Who knew it had a name?! I have this, and have always hated it as well. I have to say that once I lost my saddle bags (thank you Butts and Guts), this area did not look as noticeable. I Still have it to some degree, since it is my bone structure, but it looks much better since I have worked my legs twice a week.
There isn't a way of filling in the dip. You can only reduce the layer of fat that is above or below the dip. Hope that makes sense!
Try working out your legs twice a week. It took me a good six months, but I saw a huge difference in this area. I even lost a pant size! Muscle takes up less space!