I believe it's the runway in use, if I understand your question correctly. They'll be routed from the South if landing on 4R, from the North if landing on 22L. ARTC decides this approach long before the bird gets anywhere near the airport. The pilot is usually given the option to land on 29, remembering that 29 is the shorter runway - depending on the type of aircraft, it's weight, etc. He/she can choose the 29 approach or the runway that's in current use. Hope this helps!
LINE UP AND WAIT