L5-S1 is the exact spot where the lumbar spine ends and the sacral spine begins. The lumbosacral joint connects these bones.

Methods A total of 116 patients referred with symptoms of lumbar ... % CI 1.06–37.21) for L4, 1.74 (95% CI 1.04–2.93) for L5, and 1.29 (95% CI 0.97–1.72) for S1 nerve root impingement.

Or have you had a sudden numbness or pins-and-needles sensation in your legs or feet that you can’t explain?These are not ...

The lumbosacral plexus is formed by the ventral branches of the second to fifth lumbar nerves ... syndrome of the posterior thigh, sciatic nerve injury from intramuscular injection or projectile ...