Spine Levels—S1

Between L5-S1 or between S1-S2?

L5-S1.

Hey wait a minute, you say. Lumbar roots exit below their respective vertebrae !

Right you are. But the foramen through which they exit is above the respective disc space, so herniated lumbar discs typically hit the NEXT ROOT DOWN as it is exiting the NEXT FORAMEN DOWN. Sneaky, I know, but the angel who designed this system didn't want just anybody operating on it.

But you should operate at the right level if you want to find the disc. Thus...

L4-L5 discs cause L5 radiculopathy
L5-S1 discs cause S1 radiculopathy

...the two most common lumbar radiculopathies.