I had OSD as a young teenager too (less prevalent in girls, but still quite a few cases) and still have a noticeable lump on both knees. I have always found kneeling uncomfortable.
I do get an ache below the knees after a long run, or a long hillwalk, as if the muscle/ligament just below the kneecap was being pulled hard. However, it doesn't seem to get worse with additional training, and in fact is probably better now that I have increased my mileage.
It sounds as if your problem may not be related to OSD, but your GP should be able to tell you more.