Nerves and blood supply of lower limb

Arterial Tree - Blood on the Tracks

• Path: External Iliac → Femoral → Popliteal → Anterior/Posterior Tibial Arteries.
• Femoral Artery: Enters via femoral triangle. Main branch is the Profunda Femoris (deep thigh).
• Popliteal Artery: Deep within the popliteal fossa; gives off genicular branches to the knee.
• Anterior Tibial Artery: Supplies anterior leg compartment; continues as Dorsalis Pedis artery on the foot dorsum.
• Posterior Tibial Artery: Supplies posterior/lateral compartments; gives rise to Fibular Artery and terminates as Plantar Arteries.

⭐ The Dorsalis Pedis pulse is palpated just lateral to the extensor hallucis longus tendon. A weak or absent pulse can be a sign of peripheral arterial disease.

Venous Drainage - The Great Saphenous

• Origin: Forms from the dorsal venous arch of the foot.
• Course: Ascends anterior to the medial malleolus, up the medial side of the leg and thigh.
• Termination: Traverses the saphenous opening in the fascia lata and drains into the femoral vein.
• Tributaries: Receives blood from superficial epigastric, superficial circumflex iliac, and external pudendal veins near its termination.

⭐ Clinical Pearl: The Great Saphenous Vein is commonly harvested for coronary artery bypass grafting (CABG). Its valves must be reversed or destroyed so blood flow is not obstructed.

Lumbar Plexus - Anterior Command Center

• Roots: L1-L4 (contribution from T12).
• Key Nerves & Functions:
  • Femoral (L2-L4): Motor to anterior thigh (quadriceps); sensation to anterior thigh & medial leg.
  • Obturator (L2-L4): Motor to medial thigh adductors; sensation to medial thigh.
  • Lateral Femoral Cutaneous (L2-L3): Sensation to anterolateral thigh.
  • Genitofemoral (L1-L2): Sensation to upper medial thigh & genitalia.

⭐ Meralgia Paresthetica: Compression of the Lateral Femoral Cutaneous nerve under the inguinal ligament causes burning pain and numbness in the lateral thigh.

Sacral Plexus - Posterior Powerhouse

• Roots: Ventral rami of L4-S4.
• Location: Anterior surface of the piriformis muscle.
• Key Nerves:
  • Sciatic Nerve (L4-S3): Largest nerve in the body; supplies posterior thigh.
  • Superior Gluteal Nerve (L4-S1): Innervates gluteus medius & minimus (hip abduction/stabilization).
  • Inferior Gluteal Nerve (L5-S2): Innervates gluteus maximus (hip extension).
  • Pudendal Nerve (S2-S4): Innervates perineum; sensation from external genitalia.

⭐ Clinical Pearl: Injury to the Common Peroneal Nerve, often at the fibular neck, causes foot drop (inability to dorsiflex) and loss of sensation on the dorsum of the foot.

Clinical Correlations - Nerve Injury Clinic

• Common Peroneal: Foot drop (impaired dorsiflexion/eversion), sensory loss on foot dorsum. Vulnerable at fibular neck. 📌 PED: Peroneal Everts & Dorsiflexes.
• Tibial: Cannot stand on tiptoes (impaired plantarflexion/inversion). 📌 TIP: Tibial Inverts & Plantarflexes.
• Femoral: Weak leg extension (quadriceps), ↓ patellar reflex.

⭐ Foot drop is the most common mononeuropathy of the lower limb, typically due to common peroneal nerve compression at the fibular head.

High-Yield Points - ⚡ Biggest Takeaways

• Common peroneal nerve injury at the fibular neck causes foot drop (loss of dorsiflexion/eversion).
• Sciatic nerve is vulnerable to improper gluteal injections or posterior hip dislocation.
• Femoral nerve damage impairs knee extension and sensation over the anterior thigh.
• Tibial nerve injury prevents plantarflexion and inversion; patients cannot stand on tiptoes.
• The femoral artery is the primary arterial supply, continuing as the popliteal artery.
• The great saphenous vein is the standard vessel for coronary artery bypass grafts (CABG).