my l4/l5 discs are over 30% gone (as of 3 years ago, possibly more now)
short version i was nationally competitive powerlifter with elite totals. what began with a small pain turned into massive injury. could not train for over 8 months, i had a fucking cane and was extremely depressed. was told that i needed surgery to fuse discs together and add something that would be fabricated to give support. was told i would lose quite a bit of flexibility.
also was told i would never be able to lift again without surgery, with surgery i would be able to but not compete... tried chiropractors, phys therapy, you name it but nothing corrected it. i declined surgery and began rehabbing with a sled similar to a prowler just walking it, then adding weight over time. within a few months i was able to run slowly with it.
fast forward 3 years. my back feels fine with the exception of a few days when it may hurt on one side or the other but nothing too bad, and while im not pulling in the 700s anymore i can pull a low/mid 6 but it is very uncomfortable. rarely do i go above 5 and things are good. some things i still can not do such as heavy-medheavy back squats and heavy snatches but everything else is fine.
to answer your question i would say before continuing with lifting you need to make your lower back incredibly strong. this can be done without heavy weight. last time i went to ortho his guess was that my back muscles around the 2 discs that have deteriorated have become so big and functionally strong that they are supporting and protecting them well enough to keep me injury free.