Knee pain when pressure is taken off of foot and when bending?

i woke up yesterday morning and was coming down the steps and i was suddenly in overwhelming pain in my knee, right above my kneecap on the inside. to me, it almost felt as if something was lodged there, rubbing against whatever it is in the joint allowing it to bend properly. i figured i'd take some advil and lay down and it'd go away. but it hasn't. and i was laying down and went to lift my foot off the bed and even more pain. and as of now, my knee is just aching terribly. i haven't had any recent injuries to it, so i'm not sure it could be that. it's just really strange and i'm not sure what to make of it.