British stairs

Are the knees the first to go?
My knees feel creaky. It can hurt to walk up the steep stairs in our flat here.
We have two sets of steep steps, one as soon as you walk in to get to the main level of the apartment and then another set leading to our attic bedroom.
This morning, before dawn, I slipped down the stairs from our bedroom as I was coming down to turn the heating down. I was hot.
And I slipped. And I'll get bruises on the back of my thighs.
Anyway, I may be getting too old for steep steps.
The house we were lucky to have sold in the States was all on one level -- a rambler. Our bedroom, the kitchen, the living room, dining room, kids' rooms -- all on the same floor. Downstairs was the basement and the laundry room. After the boys' left for college, days would go by without us going down there.
I remember when we bought it, 12 years ago, my husband liked it because it was all on one floor, saying it's easy to be all on one level.
I remember thinking that was absurd at the time, considering we were in our early 40s with school-aged boys. And then I kinda hankered after a Colonial, with its stairs right when you walk in.
Now, that we've sold our house, and we live in a flat with not one, but two sets of steep steps (why?), I know what he means.
It was really nice to be on one level.
I miss it.
And I think it's my future.