Oddly I have never had an issue with PHX at either terminal.
Each time I explain that I am unable to comfortably raise my arm, the TSA employee asks me to demonstrate the height at which I can raise my arm too. (PHX is the only airport where they do ask me to show the height I can raise my arm too however)
After showing the employee the height I am capable of raising my arm too, they have always directed me to the metal detector. In fact, last time the TSA employee asked me where did I have the surgery done. I said Miami and he said that he had his done in the Phoenix area (apparently by the Ortho surgeon to the Phoenix Suns) and that it was also semi-successful.
He gave me a tip which helped him gain some more mobility and wished me a pleasant flight, so I am not sure if I am getting lucky or what, but chollie you are not experiencing what should be the procedure.
Dan