It comes on randomly, even without having done any physical activity or anything out of the regular. I am 23 yrs old and shouldn't be having pains like this so soon. It hurts for hours up to days at a time. Thought it could be irritable leg syndrome or something like that, but im not really bothered at night by it. Though it is VERY uncomfortable, and also adds difficulty to being on my feet like for my job. Sometimes I feel as if it makes my knees swell, they end up very painful as well.