As always great job Leesa!

The L3/4 Disc has herinated due to the extra pressure it absorbed from non moving discs below it ie the fused locations. It is very common and the term used is domino effect. It is a relatively small herniation at this time, but it will grow in size due to the nature of thing in that area now! Also remember when you have an MRI you spine is unloaded, meaning NOT bearing weight upon it. You could see that 2.8 turn into a 5.0 easily! This is a problem I have within the medical community when they reach a diagnosis solely on a reading instead of using that as a tool!

The other part, and IMHO, is where you are having your most pain. It is scar tissue so to speak and it is trying to grow and as with most any healthy tissue it tries to feed itself with blood and innervation which can be quite painful in itself. What has happened here, it seems, is that the nerve is becoming entrapped within this. That can be a problem, and that can be a real source of pain.

Best of luck!