My daughter suffering w/ osgood schlatter wears supportive brace, ices leg, tried motrin gave her diahreaa, changed to naproxen same result now what?

Common side effect. Diarrhea is a side effect of any NSAID. You could try Tylenol (acetaminophen) for pain, but it may not be as effective. Unfortunately the best treatment for OSD, is to stop doing the activity that makes it hurt until the pain goes away. I'd discuss your options with her orthopedist.