Sacral Plexus Diagram – Roots, Sciatic Nerve and Branches

All 14 parts on the diagram

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Roots 6

L4 root Only part of L4 joins the sacral plexus. It meets L5 to make the lumbosacral trunk.
L5 root Joins the part of L4 above it to make the lumbosacral trunk.
S1 root The first sacral nerve. The sacral nerves S1 to S4 are the basis of the plexus.
S2 root The second sacral nerve. It feeds the sciatic nerve and sends a strand to the pudendal nerve.
S3 root The third sacral nerve. It is the lowest root of the sciatic nerve.
S4 root The fourth sacral nerve. It is the lowest root of the plexus and joins the pudendal nerve.

Nerves 8

Lumbosacral trunk Part of L4 and all of L5 unite in it. It runs down into the pelvis and links the lumbar plexus with the sacral plexus.
Superior gluteal nerve Roots L4, L5 and S1. It supplies gluteus medius, gluteus minimus and tensor fasciae latae.
Inferior gluteal nerve Roots L5, S1 and S2. It supplies gluteus maximus.
Sciatic nerve Roots L4 to S3. It is a tibial nerve and a common fibular nerve bound together, and it splits into the two on the back of the thigh.
Tibial nerve Supplies the muscles in the back of the leg. Also the sole of the foot.
Common fibular nerve Supplies the muscles in the front and outer side of the leg. Also called the common peroneal nerve.
Posterior femoral cutaneous nerve Roots S1, S2 and S3. It carries feeling from the skin on the back of the thigh. Also called the posterior cutaneous nerve of the thigh.
Pudendal nerve Roots S2, S3 and S4. It supplies the muscles of the pelvic floor and the skin of the perineum.

How this list was compiled: Every name and root level checked on 2026-09-30 against (1) TeachMeAnatomy, The Sacral Plexus (the roots, the lumbosacral trunk, the five major branches and their root levels), https://teachmeanatomy.info/lower-limb/nerves/sacral-plexus/; (2) Wikipedia, Sacral plexus and Lumbosacral trunk, text only, and Gray, Anatomy of the Human Body, 1918, The Sacral and Coccygeal Nerves, https://www.bartleby.com/107/213.html (Wikipedia's account follows Gray, so the two count as one source); (3) OpenStax Anatomy and Physiology 2e, section 13.4 The Peripheral Nervous System (the plexus comes from L4, L5 and S1 to S4; the sciatic nerve is the tibial and fibular nerves together), https://openstax.org/books/anatomy-and-physiology-2e/pages/13-4-the-peripheral-nervous-system. Licence: own work

The drawing: Drawn for this site on 2026-10-05 by script. The outline of the hip bone is plotted after fig. 320 (Articulations of pelvis, posterior view) and the femur after fig. 245 (Right femur, posterior surface) of Henry Gray, Anatomy of the Human Body, 20th edition, 1918 (public domain; https://commons.wikimedia.org/wiki/File:Gray320.png and https://commons.wikimedia.org/wiki/File:Gray245.png); the sacrum follows fig. 96 and the courses of the nerves follow figs. 828 and 832 of the same book, by eye. A plan laid over the bones, not to scale: the nerves are spread out, the sciatic nerve splits higher than in the body, and the sacral roots are drawn on the back of the sacrum so they can be seen. In the body they leave by the openings on its front, and the plexus lies in front of the bone. Licence: own drawing; hip bone and femur outlines after public domain plates

How it works

This plan shows the right sacral plexus in posterior view, drawn over the sacrum and hip bone. The nerves are spread out so each can be followed from its roots.

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Follow each nerve back to its roots

Numbers 1 to 6 are the roots, from L4 at the top to S4. L4 and L5 join as the lumbosacral trunk (7), which meets the sacral roots in a band. The band goes on as the sciatic nerve (10), which splits into the tibial (11) and common fibular (12) nerves. The other four are the gluteal nerves (8 and 9), the posterior femoral cutaneous nerve (13) and the pudendal nerve (14).

The upper of the two forked nerves is the superior gluteal; the lower is the inferior gluteal.
The pudendal nerve takes the lowest roots: S2, S3 and S4.

Questions and answers

Which nerves arise from the sacral plexus?

Five major nerves: the superior gluteal, the inferior gluteal, the sciatic, the posterior femoral cutaneous and the pudendal. The sciatic nerve then divides into the tibial and common fibular nerves. There are smaller branches to nearby muscles as well.

What are the roots of the sacral plexus?

The anterior rami of sacral nerves S1 to S4, joined by lumbar nerves L4 and L5 through the lumbosacral trunk. That is why the plexus is often written L4 to S4.

What are the roots of the sciatic nerve?

L4, L5, S1, S2 and S3. The sciatic nerve is really two nerves in one sheath, the tibial and the common fibular, and it separates into them on the back of the thigh.

What is the lumbosacral trunk?

A thick cord formed by part of L4 and all of L5. It runs down into the pelvis to join the sacral roots, so it links the lumbar plexus to the sacral plexus.