Hi about 5 nights ago I was woke up in the middle of the night with a terrible sharp pain at the back of my leg right behind my knee. It was so painful that I had to get out of bed and try to stand up which I could not do easily as I could not put weight on that leg proproperly. The pain shot down my let to my foot and then shot up to the top of my thigh. After a few minutes it felt a lot better and things seemed to go back to normal (more or less) - although the leg felt a little odd. Since then I have been quite careful and have even put a pillow in my bed to support the let at night. I was just beginning to feel much better and now this evening my let is hurting again - feels like a dull ache that gets worse in waves. What could this be? Thanks for your help