A seat assembly for a motor vehicle includes a seat back and an armrest rotatably coupled to the seat back for movement between a generally vertical, stowed position and a generally horizontal, use position. A guide member is disposed between the armrest and the seat back. The guide member includes a tube having an interior defining thread ridges. A guide pin extends through the tube and interconnects the armrest and seat back. The guide pin includes a helical screw thread portion for rotatably engaging the thread ridges to provide for lateral adjustment of the armrest towards and away from the seat back as the armrest moves between its respective stowed and use position.