Can i have osgood schlatters and tendonitis at the same time. what would the orthopedic doctor do for them both?

Heat, ice meds: No surgery. The standard therapy would be heat, ice, acentaminophen, NSAIDS like ibuprofen, naproxen. When the growth plate closes this pain will resolve. Since you have tendonitis also this could explain why you have pain beyond the presence of a closed growth plate. Physical therapy may be a good addition to your therapy.

Treatment: the treatment consists of rest and non involvement of activities for up to six months if necessary. Physical therapy and pain killers may be needed

No, U cannot have --: both at the same time, as the OS disease becomes quiescent after 12-13 yrs of age (although the bump will remain for ever), but the Tendonitis can occur, at any time. The Orthopod will confirm the Dx and start treatment and F/U till all subsides and you recover completely. Good Luck.