I was diagnosed with degenerative discs between S1/L5, L5/L4 over 25 years ago. I was very big on jumping/bounding sports and had suffered several falls from heights over 10 feet (including landing on the edge of a swimming pool in a seated position from a fall from a ten foot pool slide which I think started the whole degenerative process). I was given no restirctions other than avoiding any activity that caused me to spasm or produced pain. I found that I could still do a lot of things I liked, but the amount of concentration it took not to aggravate the low back muscles led me to give up jumping and jumping sports (jumping down when hiking, basketball, spring board diving, etc.). I have learned and now habitually maintain proper posture and stability. There is a possibility that some of my other discs have degenerated as I notice similar symptoms at other sections of my spine, but they are not debilitating as I know how to deal with the issues. And I have not persued diagnosis further as there is nothing to be done about them that I am not doing.
I have also worked with numerous clients with significant degenerative disc progression. Everyone will eventually have some degree of disc degeneration, but their history will also determine the level of degeneration they now have.
I work with such clients within their physician, surgeon, and therapist recommendations and under those guidelines within the clients tolerances. There are a number of stretches and exercises that have been pretty much standard recommendations. I progress clients to the limit of the recommendations and if the client desires continued progress (rarely as most are content with getting back to their previous level of ability without pain or managed pain), I send them back to their health provider to get further clearance for what they wish to do.
As each individual can have other contributing issues and individual compression areas affecting them differently. I do not make any exercise recommendations to other trainers. You need to follow their doctor or therapists recommendations and contraindications. If you are not comfortable working with such clients, you should do your best to find an appropriate trainer to refer them to contact.