Sciatic Nerve Block


The sciatic nerve is formed by the ventral rami of L4-S3 and encompasses most of the sacral plexus (L4-S4) to provide innervation to each leg.  Along with the femoral nerve, the sciatic nerve provides motor and sensory innervation to the lower extremity and can be blocked or anesthetized at several points along its course.

  • It is the largest and longest nerve in the human body beginning at the lumbosacral nerve roots in the low back extending through the buttocks and continuing its course posteriorly down each leg to the foot and toes.


Sensory and Motor Coverage 

While the sciatic nerve does not include any muscles in the gluteal region, it does supply innervation to the posterior thigh muscles as well as all muscles of the lower leg and foot.  Sensory innervation to the entire lower leg is also via the sciatic nerve, except the medial side of the lower leg.

  • Posterior thigh
    • EXCEPTION: Sensory innervation provided by posterior femoral cutaneous nerve, a separate nerve of the sacral plexus.
    • NOTE: Femoral nerve supplies the motor and sensory innervation to the anterior thigh.
  • Entire lower leg
    • EXCEPTION: Medial lower leg sensation is supplied by the saphenous nerve, a terminal branch of the femoral nerve, so for complete anesthesia of the lower leg, the saphenous (or femoral) nerve must also be blocked.



  • Blockade of the sciatic nerve is ideal for surgeries or painful pathologies of the posterior thigh and leg.
  • The posterior cutaneous nerve is not reliably blocked due to its proximal takeoff from the sacral plexus, leaving sensation to the posterior thigh unreliably anesthetized. 
  • Surgery including the medial lower leg will require additional saphenous nerve blockade for complete coverage.


Block Technique

Location of pathology and ability (or inability) for patient to position will determine exact target location. The sciatic nerve is reliably located and blocked at different locations along its course.  Common locations include:

  • Mid-gluteal region – most challenging, deep under fat and muscles but most likely, versus more distal locations, to catch the posterior femoral cutaneous branches coursing parallel with the sciatic nerve in the gluteal region.  Patient positioned lateral decubitus with hip and knee flexed.
  • Sub-gluteal region – easier to perform as the nerve is more superficial, but does not reliably block the posterior femoral cutaneous branches.  Patient can be positioned prone without flexion of hip or knee.
  • Popliteal fossa – most superficial location and can be used to block the entire lower extremity (except medially) if the nerve is blocked before it splits into its two components, the tibial and common peroneal nerves.  Patient can be positioned supine, lateral or prone.

Block Duration

  • Sciatic nerve blocks require adequate set-up because this large nerve resists local anesthetic penetration, leading to longer block onset times.  
  • Duration of the block will depend on the properties of the local anesthetic chosen.  
  • Catheters can be placed and secured for continuous infusion.

Special Considerations

Contraindications and Side Effects

  • Coagulopathy
  • Pre-existing motor or sensory deficits
  • Infection at site of block
  • Consider avoidance where sensory blockade might mask compartment syndrome
  • Side effects are similar for any regional anesthetic technique including:
    • Block Failure
    • Hemorrhage, bruising, hematoma
    • Infection
    • Nerve damage
    • Local anesthetic (LA) toxicity
    • Allergy to LAs
  • Caution against bearing weight on the blocked lower extremity for 24 hours due to possible hamstring weakness and risk of falls
  • NOTE: While LA absorption from sciatic nerve block is minimal, it is important to remember that the inferior gluteal vessels are large and multiple, therefore hematomas could develop. Repositioning the patient supine immediately post block could theoretically help to decrease the chance for a hematoma to develop after gluteal sciatic blocks.

Defense and Veterans Center for Integrative Pain Management, Chapter 17: Sciatic Nerve Block: Posterior and Alternative Approaches.

NYSORA Textbook of Regional Anesthesia and Acute Pain Management Hadzic A et al. McGraw-Hill, 2007, Chapter 37.

Atlas of Ultrasound-Guided Regional Anesthesia, Gray A et al. Elsevier, 2019, 3rd Edition, Chapter 44: Sciatic Nerve Block.