I knocked my knee a about 3 weeks back during Tough Mudder, it was sore like a bruise for a week, but I was still able to exercise, then about a week ago i moved my knee cap around before bed and the next day and days since its been quite sore when I go to stand up. Its fine when I sit down, I can walk, but down hill and stairs is hurts a bit, there is kind of a click/crunch kind of feeling sometimes when I stand up.