I have the same problem with L4&5 which gave me spinal stenosis and NP.
I’m numb from knees down with burning pain just above my knees. I went through gabapentin, pre gab etc.
nothing worked. A dulox helped some, it’s an anti depressant. Then my pain doctor and I tried lumbar injections. She injected both side of the pain nerves exiting the lumbar region using fluoride for guiding the needles.
The pain was gone!