Glad you liked the photos, Catrin! I haven't even had a chance to look at the ones my DH took yet. Of course it looks even better in person.
On your question, I am not sure I know what a steep vertical "step down" is as opposed to a steep incline/decline. Could you elaborate? The trail definitely had some steep sections but nothing that tough until the very end. The last 1/4 miles was very steep, with loose rocks and sandy soil. It was not rock scrambling, though, more like a gravel road on steroids. I think my DH got a photo of it, so I will look and post back here if so.
One place you might consider is Bryce Canyon NP. We found the hiking trails there very manageable compared to some of the other places we hiked in the southwest. We also found Arches to be not bad. Canyonlands and Zion were both tougher, and of course the grandaddy of them all, the Grand Canyon -- definitely not for those with knee problems.

