@jimk849 I think stairs are one of the last things that feel good. It took a long time for me to be able to walk up and down stairs without holding the rail, and at times, for instance when I am particularly tired, I still feel a bit unsteady. When you go up or down a stairway all of your weight is on one leg then the other, so it does make sense. How long ago was your knee replacement? I am sure this will gradually get better with time.
JK