I just had my left knee replaced June 30th. Had the right one done 2009 or 2010. I can't knee comfortably for any amount of time. This was one of my biggest worries when getting up from the floor. My doctor said they aren't really meant to be kneeled on.
I waited on this one because I didn't like the thought of not being able to get up if I fell down.
I Googled it and did not get a definitive answer. In any case I wish you all the best in your recovery. Physical therapy and keep that knee going. Bend and stretch every time you think of it.