Im on the comeback from 3 prolapsed discs & need a squat replacement - im currently doing overhead squats, but im thinking roman chair squats would be even better (as in strengthening quads whilst lowering stress on the lumbar), similar to above
http://www.tmuscle.com/free_online_article//bulletproof_that_back read all 3
I have been doing hip belt squats a lot the past few months and have grown to like them a lot. They are awkward at first but once you get used to them they will torch your quads without putting pressure on your low back. I bought a hip belt from Ironmind but you could also use a dip belt.
Here's what they look like.
I also would try some single leg work with dumbells.
Hope you feel better and good luck