Changes in the geometric properties of the joint with wear occur slowly for a lower pair. At least as important are the simple geometries of the relative motions that these joints permit.
I don't understand the last sentence.
In that sentence, "at least as important as" compares:
The meaning is that the geometries:
From the Cambridge Dictionary
at least = as much as, or more than, a number or amount:
- It will cost at least $100.
- It will be £200 at the very least.
- You'll have to wait at least an hour.
Also from Cambridge Dictionary
As … as = We use as + adjective/adverb + as to make comparisons when the things we are comparing are equal in some way:
- The world’s biggest bull is as big as a small elephant.
- The weather this summer is as bad as last year. It hasn’t stopped raining for weeks.
- You have to unwrap it as carefully as you can. It’s quite fragile.