Which nerve root contributions form the sciatic nerve?

• A. L2-L4
• B. L4-S3
• C. L3-S2
• D. L5-S1

Answer: (B)

The sciatic nerve is formed from the ventral rami that contribute to the lumbosacral plexus, specifically from L4 through S3. These roots join to make the single, thick nerve that travels through the gluteal region, down the posterior thigh, and eventually splits into the tibial and common peroneal nerves near the knee. Because the contributing roots span L4, L5, S1, S2, and S3, this is the correct range for the sciatic nerve.

Understanding this helps explain why injury at these roots or to the sciatic nerve affects large portions of the leg. If the root contributions were limited to a different range, or started later or ended earlier, the formed nerve would not be the sciatic nerve as it courses through the thigh and leg.