This is a bit weird, but when I am first waking up my knees hurt to bend. I keep them warm at night, so it is not as if they are just tight from being cold. We are talking serious pain. I generally sleep on either my stomach or back with my legs straight. Once I get up and walk for a couple of seconds, the pain goes away. I do a couple of football like drills to see how my knees fell, and they are just fine. The thing that concerns me is that my joints only bother me when there is extreme weather change. I am 24, I have no arthritis, I am 300lb powerlifter and I do quite a bit of running. I am currently not training and I haven't been powerlifting since September. Any thoughts on what this might be? Minor Ligament injury or something?