Leg routines huh? Well that is a whole can of worms, my first. I will get into it. First lets talk back issues. If you have low back problems. best bet is to find out what is going on. I can speak on my issues, which are in the muscle and effect my SI but if you have ruptured disc problems, it might take more rehab. I found that my low back had gotten very weak and would spasm when it would contract. Over time, I built it up with lightly banded hypers and then light rack pull deads. Over time, I was able to increase weight. As long as I keep my low back strong, I can do pretty much anything I want.
For leg training, squats have done a lot for me, but I had to back down the weight and relearn form. I went to body weight squats and learned how to make them hard, so that the tension all goes to the quad muscles. This further strengthened my low back as well as trained my quads to fire better. I learned how to make these body weight squats HARD. Then from there, when I went back to weighted squats, I took my new form with me. Legs started to grow and since I learned how to really fire the muscles, I have been able to use much less weight, which saves my back.
I also prefatigure my quads and hams before I do compound lifts. This helps me get much more out of my bigger lifts, while keeping the weights down. Here is an example of what I might do for quads. Also, note that I have a seperate quad and ham day. Since I can't bring the intensity I would like, 2 workouts make up for it. So heres a quad day. I change them each week
seated ham curls 5x 10, 2 second squeeze
Free weight BB squats 4x8-12, 2x20
Leg press 5x25
walking Lunges 2 sets to failure