If this helps at all, my physiotherapist recently told me that static lunges are much, much better for the lower back, than moving lunges (and especially step-back lunges). She doesn't advocate anything except for static lunges, even for people who have no back issues. Moving lunges put too much shearing in the lower back, apparently. So, if you prefer the static lunge over the moving lunges, there are good medical reasons for doing so.
Cheers,
Sandra