My dodgy knees aren't keen on steps generally, and ladders are right out. We have a nice solid step like this:
Ours is actually most of the width of the tent and deeper so it is easy to stand on and functions as a seat and a bench as well. It has a bit of steel tubing at each end which slots into tubing on the trailer, and there are zips in the tent at the appropriate spot (although I have also seen it with just holes cut in the canvas). So it goes in easy and is solid as. It travels on the bed.
This step is just a little far off the ground for me, so I also have one of those small foldable single steps to get up onto this. Getting from the big step to bed is quite easy, as it involves a leaning motion rather than stepping. Getting off the bed is exactly like getting out of the fourby - aim feet at appropriate point and slide off.
Depending on your flexibility this might not suit, but I found the standard folding steps were a bit unstable when I have tried them, and I was pretty sure I was going to go for a tumble at some stage.