20yr f "growing pains" at night underneath and around knee caps for 1 yr. fell a few months ago one 1 knee with no injury but bruising. just walk.

Patellofemoral pain: With your age and no history of injury and w/out any other information or a physical examination the most likely cause of your pain is your kneecap( patellofemoral). The cartilage beneath your kneecap can soften and cause pain esp. W/stair climbing , stair master , lunges, squats , or just keeping your knees bent for a period of time( sitting in an airplane, church etc).Anatomy, weight, jt. Laxity.