56 Neuroanatomy: Draw It to Know It
■ Th e common peroneal nerve divides into the deep
peroneal nerve and superfi cial peroneal nerve.
■ Th e deep peroneal nerve innervates tibialis anterior
(L4, L5), extensor digitorum longus, extensor hallucis
longus, peroneus tertius, extensor digitorum brevis,
and extensor hallucis brevis (L5, S1).
■ Th e superfi cial peroneal nerve innervates peroneus
longus and peroneus brevis (L5, S1).
■ Th e major tibial-innervated muscles are the
gastrocnemius and soleus (S1, S2), tibialis posterior,
fl exor digitorum longus, and fl exor hallucis longus
(L5, S1).
■ Th e sural nerve is formed from branches of the
common peroneal nerve and the tibial nerve.Know-It Points
Lumbosacral Plexus
■ Th e lumbosacral plexus is formed from L1–S4.
■ Th e sciatic nerve (L4–S3) innervates the posterior
thigh.
■ Th e femoral and obturator nerves (L2–L4) innervate
the anterior thigh.
■ Th e peroneal nerve (L4–S2) innervates the anterior
and lateral leg and dorsal foot.
■ Th e tibial nerve (L4–S3) innervates the posterior leg
and plantar foot.
■ Th e lateral cutaneous nerve of the thigh (L2, L3)
provides sensory coverage to the lateral thigh.The Leg & Foot
The Thigh
■ Th e femoral nerve innervates the anterior
compartment (L2–L4).
■ Th e obturator nerve innervates the medial
compartment (L2–L4).
■ Th e sciatic nerve innervates the posterior
compartment (L4–S2).
■ Th e femoral nerve innervates the quadriceps femoris
muscles and we also consider it to innervate the
iliopsoas (see text for details).
■ Th e obturator nerve innervates the adductor
muscles.
■ Th e sciatic nerve innervates the hamstrings muscles.
■ Within the femoral triangle, the nerve lies most
laterally; medial to it is the artery; and medial to it is
the vein: use the mnemonic NAVY.