I went to an amusement park yesterday. I noticed a bit of pain earlier in the day on what I'm not sure is my leg or my knee - it's off the side of me knee. Later on, I was walking down a hill, and the pain was so bad, I could barely do it. It shot all the way down my leg. It got better in a little while, but never completely went away. Every time I get up from sitting down since then, the pain is really bad whenever I bend my leg. It's especially bad when I go up or down a hill. What's going on with my leg?!