Prolapse of veebral disc between L5-S1 will affect which nerve root
L4
L5
S1
S2
Since most disc herniations occur posterolaterally, the root that gets compressed is actually the root that exits the foramen below the herniated disc. So, a disc protrusion at L4/L5 will compress the L5 root, and a protrusion at L5/S1 will compress the S1 root . Ref - sciencedirect.com
General anatomy