My school has been doing something called a health kick where we have to run (fartlek training) for 23 minutes 3 times a week. I m quite skinny and don t have much muscle on my knee. My knee has started to click when you move it at an angle when it didn t do that before. I had knee pain two years ago climbing stairs at times but thought my knee was stiff as it only happened sometimes. No it s happening more often and it sometimes hurts it I bend my knee. I sometimes feel like my knee is going to give up on me when going downstairs. It hurts more often when climbing the stairs. The side of my knee is a bit shallower than the other one. It feels hotter around the knee and my feet are white when my other foot has more colour in it. My knee has also sometimes started to ache when I sit. The pain goes away when I run but comes back minutes after. I can t stand on one leg for long without it having a sharp pain in the inside.