Why Does One Experience Pain In The Knees During Night?

I have a knee problem that I've had almost a year now. On a night and mainly only on a night do my knees burn up and start to feel rsuty when I move them. I am into intensive sport and have been for two years. When i seeked for help from my GP and a specailist(rhoematologist) they could not find a problem. I think this could be because, when I see them, it's during the day and my knees arn't red and burning up so they can't see anything.



Sorry for making it that short, but I really need your help! The pain can get quite unbearable and can last all night