Milk gets trapped behind my Philips Avent massage cushion

Try leaning slightly forward when pumping. If there is still milk behind the cushion, remove and re fit the let down massage cushion to ensure it is firmly attached and pushed far enough down the center of the funnel. Some may prefer to use the pump without the let down massage cushion. The let down massage cushion has petals that flex in and out to gently massage the area around the breast. This is intended to stimulate a fast, natural milk flow.