Sciatic Nerve

Q: Which nerves form the sural nerve?

The sural nerve (n. suralis) is formed in the leg by the union of the medial sural cutaneous nerve (from the tibial nerve) and the lateral sural cutaneous nerve (from the common fibular nerve).

Nervus ischiadicus

For medical students2 min readUpdated 2026-10-10

The sciatic nerve is the largest nerve trunk in the human body, formed by the L₄–S₃ spinal segments. It provides motor innervation to the posterior compartment of the thigh, while its terminal branches are entirely responsible for the sensory and muscular innervation of the leg and foot.

Spinal segmentsL₄–S₃

Muscular branches (thigh)Posterior compartment muscles and adductor magnus

Articular branchesHip and knee joints

Terminal branchesTibial and common fibular (peroneal) nerves

Pelvic Exit and Thigh Topography

Formed from the roots of the sacral plexus, the sciatic nerve (n. ischiadicus) leaves the pelvic cavity through the greater sciatic foramen inferior to the piriformis muscle (foramen infrapiriforme). Immediately upon exit, it lies deep to the gluteus maximus muscle.

Descending along the posterior aspect of the thigh, the nerve trunk gives off several motor branches. These supply the posterior compartment muscles, which include the biceps femoris (m. biceps femoris), semitendinosus (m. semitendinosus), and semimembranosus (m. semimembranosus). In addition, the adductor magnus (m. adductor magnus) receives innervation from the sciatic nerve. Along its course through the thigh, the nerve also emits sensory articular branches directed to the hip and knee joints.

Bifurcation of the Sciatic Nerve

Upon reaching the popliteal fossa (and in some anatomical variants significantly higher), the main trunk of the sciatic nerve divides into two major terminal branches:

Tibial nerve (n. tibialis).
Common fibular nerve (n. fibularis communis / peroneus).

Common Fibular Nerve and its Branches

The common fibular nerve (segments L₄–S₂) courses laterally and winds around the neck of the fibula. Even before its main division, it gives off the lateral sural cutaneous nerve (n. cutaneus surae lateralis), which innervates the skin of the anterolateral leg. Subsequently, the common trunk divides into two branches:

Superficial fibular nerve (n. fibularis superficialis). It runs within the lateral compartment of the leg, then pierces the deep fascia to enter the subcutaneous tissue. It supplies cutaneous sensation to the anterolateral leg, as well as most of the dorsal foot and dorsal toes (except for the first web space). Its terminal branches are the dorsal digital nerves of the foot (nn. digitales dorsales pedis).
Deep fibular nerve (n. fibularis profundus). It descends along the anterior surface of the interosseous membrane. Its cutaneous innervation zone is extremely limited: a narrow strip of skin strictly between the 1st and 2nd toes (the first web space).

Tibial Nerve and Sole Innervation

The tibial nerve (n. tibialis, segments L₄–S₃) continues through the popliteal fossa and the posterior leg. It gives off the medial sural cutaneous nerve (n. cutaneus surae medialis), which then joins the lateral sural cutaneous nerve to form the single sural nerve (n. suralis). This nerve innervates the skin of the posterolateral leg, the lateral edge of the foot, and the 5th toe.

After passing posterior to the medial malleolus, the tibial nerve enters the sole of the foot and divides into two branches:

Medial plantar nerve (n. plantaris medialis). It innervates the skin of the medial sole, digits 1 through 3, and the medial half of the 4th digit. Along its course, it emits common plantar digital nerves (nn. digitales plantares communes) and proper plantar digital nerves (nn. digitales plantares proprii).
Lateral plantar nerve (n. plantaris lateralis). It supplies sensation to the skin of the lateral sole, the 5th digit, and the lateral half of the 4th digit via proper plantar digital nerves.

Summary: Cutaneous Innervation of the Dorsum of the Foot

Cutaneous innervation of the dorsal surface of the foot is supplied by several nerves with clearly demarcated zones:

Main area of the dorsal foot: innervated by the superficial fibular nerve (n. fibularis superficialis).
First web space: narrow zone supplied by the deep fibular nerve (n. fibularis profundus).
Lateral margin of the foot: innervation zone of the sural nerve (n. suralis).
Medial margin of the foot: supplied by the saphenous nerve (n. saphenus).

Mnemonic

To quickly remember the innervation of the foot dorsum: “Deep hides in the first cleft” (the deep fibular nerve innervates only the 1st web space), while “Superficial covers all the rest” (the superficial fibular nerve supplies the main part of the dorsum).

Frequently asked questions

Which muscles of the leg does the tibial nerve innervate?

The tibial nerve innervates the posterior compartment muscles of the leg, which act as plantar flexors of the foot and flexors of the toes. These include:

Popliteus muscle (m. popliteus)
Plantaris muscle
Triceps surae (includes gastrocnemius and soleus muscles)
Tibialis posterior
Flexor digitorum longus
Flexor hallucis longus

Which muscles does the deep fibular nerve innervate?

The deep fibular nerve innervates the anterior compartment muscles, which act as dorsiflexors of the foot and extensors of the toes. These include:

Tibialis anterior
Extensor digitorum longus
Extensor digitorum brevis
Extensor hallucis longus
Extensor hallucis brevis

Which muscles does the superficial fibular nerve innervate?

The superficial fibular nerve innervates the lateral compartment muscles of the leg, specifically:

Fibularis longus (m. fibularis longus or m. peroneus longus) — performs plantarflexion and eversion of the foot, lowering its medial border.

Which foot muscles do the plantar nerves innervate?

The plantar nerves innervate the intrinsic muscles of the foot, dividing into medial and lateral branches.

Nerve	Innervated Muscles
Medial plantar nerve (n. plantaris medialis)	Muscles of the great toe, flexor digitorum brevis, two medial lumbricals
Lateral plantar nerve (n. plantaris lateralis)	Muscles of the 5th digit, adductor hallucis (m. adductor hallucis), quadratus plantae (m. quadratus plantae), two lateral lumbricals (mm. lumbricales), all interossei (mm. interossei)

At what level does the sciatic nerve divide into its branches?

Classically, division into the tibial and common fibular nerves occurs in the popliteal fossa. However, bifurcation can also occur higher up along the posterior thigh.

Which nerve innervates the first web space of the foot?

The skin of the first web space (between digits I and II) is innervated by the terminal branches of the deep fibular nerve (n. fibularis profundus).

Which nerves form the sural nerve?

The sural nerve (n. suralis) is formed in the leg by the union of the medial sural cutaneous nerve (from the tibial nerve) and the lateral sural cutaneous nerve (from the common fibular nerve).

Go deeper

Anatomy of the infrapiriform space and surrounding fascia
Topography of the popliteal fossa
Structure of the interosseous membrane of the leg
Branching pattern of the common and proper plantar nerves