J.J. Arrington was released by the Broncos after he failed a physical due to a balky right knee. The team confirmed the move Thursday. Arrington was one of three veteran tailbacks the Broncos brought in during the offseason, along with Correll Buckhalter and LaMont Jordan. The team had placed seven running backs on injured reserve last season. The Broncos also selected Knowshon Moreno with the 12th pick in the draft to bolster the backfield.