Lower Extremity

Lateral Femoral Cuteneous Nerve

L2-L3

Femoral nerve

L2-L4

Sciatic Nerve

L4-S3

Posterior femoral cutaneous nerve

S1-S3

Lower extremity is innervated by 2 plexuses

1. Lumbar Plexus: L1-L4 (+T12 contribution in 50% of the population.

2. Sacral Plexus: L4-S4

Lumar plexus gives rise to ___ nerves

“I Innocently Get Lit on Fridays”

6 nerves

Lumbar plexus gives rise to these 6 nerves

“I Innocently Get Lit on Fridays”

1. Iliohypogastric

2. Ilioinguinal

3. Genito-Femoral

4. Lateral Femoral Cutaneous

5. Obturator

6. Femoral (Largest branch)

Sacral Plexus gives rise to 5 major nerves

SIPPS

1. Superior gluteal n.

2. Inferior Gluteal n.

3. Posterior cutaneous n.

4. Pudendal n.

5. Sciatic n. (Arises from 2 trunk = common peroneal + tibial)

The sciatic nerve arises from 2 trunks, which are ___?

1. Common Peroneal

2. Tibial

Foot and Ankle

• Innervated by __ Nerves

Senior Student Sext During Prom 😭

5 Nerves - Senior Students Sext During Prom 😭

1. Saphenous

2. Sural

3. Superficial peroneal

4. Deep peroneal

5. Posterior tibial

Q: How many plexuses innervate the lower extremity?

A: Two: lumbar and sacral plexuses.

Q: What spinal roots form the lumbar plexus?

A: L1–L4; sometimes T12 contributes.

Q: What area does the lumbar plexus primarily innervate?

A: Anterior/front of the leg.

Q: What spinal roots form the sacral plexus?

A: L4–S3.

Q: What area does the sacral plexus primarily innervate?

A: Posterior/back of the leg.

Memory trick:

Lumbar = Look forward
Sacral = See the back

A: Lumbar = anterior/front of the leg

Sacral = posterior/back of the leg.

• Femoral nerve: L2–L4

• Obturator nerve: L2–L4

• Lateral femoral cutaneous nerve: L2–L3

• Lumbosacral trunk: L4–L5; connects lumbar and sacral plexuses

• Sciatic nerve: L4–S3; largest nerve in the body

• Sciatic nerve divides into:

  • Tibial nerve

  • Common peroneal (fibular) nerve

• Superior gluteal nerve: L4–S1

• Inferior gluteal nerve: L5–S2

• Pudendal nerve: S2–S4

Q: Where does the lateral femoral cutaneous nerve pass?

A: Under the inguinal ligament near the ASIS.

Q: What are the roots and divisions of the lateral femoral cutaneous nerve?

A: L2–L3, posterior divisions.

Q: What are the roots and divisions of the femoral nerve?

A: L2–L4, posterior divisions.

Q: Where is the femoral nerve located relative to the femoral artery?

LATERAL to the femoral artery under the inguinal ligament.

Q: What major terminal sensory nerve arises from the femoral nerve?

A: The saphenous nerve.

Q: What is the course of the saphenous nerve?

Travels through the adductor canal and becomes superficial near the knee.

What are the roots and divisions of the obturator nerve?

L2–L4, anterior divisions.

Through what structure does the obturator nerve enter the thigh?

The obturator canal.

Must memorize

• Lateral femoral cutaneous: L2–L3 posterior

• Femoral: L2–L4 posterior

• Obturator: L2–L4 anterior

• Femoral nerve → saphenous nerve

Q: Describe the sacral plexus and its most important nerve.

• sacral plexus arises from L4–S3 with possible S4 contribution.

• The L4–L5 lumbosacral trunk joins the sacral roots.

• Its largest and most important nerve is the sciatic nerve.

Q: Describe the roots, course, and branches of the sciatic nerve.

• Arises from L4–S3

• Exits the pelvis through the greater sciatic foramen below the piriformis

• Travels between the greater trochanter and ischial tuberosity

• Usually divides in the proximal popliteal fossa

• Divides into the tibial and common peroneal (fibular) nerves

Q: Compare the tibial and common peroneal divisions of the sciatic nerve.

• Tibial: L4–S3, anterior divisions; passes through the popliteal fossa between the gastrocnemius heads.

• Common peroneal: L4–S2, posterior divisions; crosses the fibular head/neck and divides into the deep and superficial peroneal nerves.