What Causes Pain In Legs, Back And Chest In 14 Year Old?

Hi this question is pertaining to my 14 year old daughter, she not the average height for her age, she s 5 11, my concerns are , lately she s been complainign about pains in her legs,back and chest, of and on, i took her to her doctor he did blood owrk and xrays to make sure she did have signs of spinal curvrage, all came back normal, but now he wants to sed her to see a Reumatologist for further testing , is that normal? or is he looking for specific someting