I am 15, and have had 7 surgeries to treat my multiple hereditary osteochondromatosis. I had a tumid removed from right above my knee in March, because an MRI showed it to have 1.5 cm of cartilage cap and we didn't want it to turn malignant in the future. It healed very nicely and I have regained full mobility (well, for me. I didn't have full mobility in the first place) . I have recently completed the summer musical I do every year, which is the most intense exercise I have done since the procedure. It has started to have a strange click where the tumor was, and is tender to the touch in that area. It is also sore to put weight on at certain times. We weren't sure if this should be cause for alarm, because sometimes problem areas flare up during times of exertion, but as soon as we get it checked out is nothing and goes away. But at the same time, this tumid was removed under more serious circumstances than before. Now, I know that the worst thing you can do is to google your symptoms, but according to the Internet (which we all know is never wrong :p) flaring up during exercise, tenderness and soreness at rest can be warning signs of osteosarcoma. Also, as an adolescent, this would be the prime time for any such ailement to develop. I don't want to believe everything I read online, but I also don't want to pass anything off. I'm just wary, because ive been to many appointments complaing of pains only for them to be nothing serious. Any opinions?