Im 23 5'2'' 115lbs. I have danced for 17 years and took a lot of hard falls and hits to my knees so that might be the original cause. They have always been fairly sore and crack every time i sit down, stand up, stretch, or turn my upper body while keeping my legs straight. Also its to a point now when it will be very stiff and painful first thing in the morning, and i cant sit indian style or kneel on them for more than a few minutes without a dull pain kicking in. Ice, heat, anti-inflamatory give temporary relief, but not much. Is it time to see a doctor?