Right after surgery you will need to do a combo elevate/ice/exercise and probably wont even want to look at a sewing machine during that time. (usually about 4-6 weeks per knee). You probably shouldn't operate a sewing machine with the narcotic pain relievers on board either. If you can arrange it so that you are elevating your leg (the surgical side) while you are sitting there, you might get away with the quilting frame, but your stitching may suffer :-)
No, I have not had my knees done (yet) but I have taken care of many patients who have had total joint surgery done. Good luck and remember that eventually you will have pain free knees at the end of it!