i gots it too, tho now i have identified that mine was triggered by striking my knee on a granite rockface whilst rockclimbing.........lol ;)
i've been taking a couple of days off, i raced on wednesday there and i took today and yesterday off, the problem gets better with time, but ibuprofen relieves the pain and reduces the swelling.
you can do straight leg excercises................... if you can find out what the hell they are, this strengthens and promotes healing.