I used to dance ballet, and do gymnastics so I used to be quit flexible. I've kept up with my stretching somewhat over the years, and while i'm not as flexible as I used to be, I'm still more flexible than most. My left side used to be the most flexible, but as of a few months ago my left leg has this horrible pain starting at the back of my upper thigh going all the way down to my ankle. no amount of stretching loosens my leg or lessens the pain. Actually, the more I stretch it, the more it hurts. It's more concentrated around the back of my knee. I've never had anything like this before, and, for whatever reason, has really gotten me down. Any idea on what this could be and how to fix it? Thanks again!