bizi, have you ever seen those gardening pads for knees? Some of them have little rails on the side as well. That might take away some strain. There are many different types and lots of images if you search 'garden kneelers'. You could also make a kneeling pad with good quality foam covered in pretty fabric. I would make you one if I lived there. lol. You could also just use an old or new cushion or pillow. You could cut down a pillow slip/case to a smaller rectangular size just for your knees and stuff it with some of the old cushion or pillow filling.