Forgive me for my non pc language. I think you know what I meant! No offense intended. I also found that a lot of arm/leg/knee warmers are sized like S/M or L/XL, so you get a "bigger" range of stretch. So if you are on the smaller end of a size, it doesn't work.
I also have knickers, but on a person as short as me, knickers are actually almost tights, with no fleecy lining! Until I found the SM knee warmers, I preferred the knickers, but now I use the warmers a lot, especially on those cool New England days that eventually warm up. I just get a lot warmer on rides now and I seem to be able to tolerate the cold more, so the knee warmers seem to be more useful. And these don't give too much of the sausage effect. However, they don't look so great with my newer Shebeest shorts, so I stick to wearing them with the Terrys.