Popliteal block

10 min read Last updated April 8, 2026

Surgical approach (context: typical foot/ankle surgery where popliteal block is used)

  • Common operations: ankle ORIF, Achilles tendon repair, hindfoot fusion, calcaneal fixation, tendon/ligament reconstruction, debridement, amputations (forefoot/midfoot), extensive foot soft tissue surgery
  • Patient positioning: supine with leg externally rotated (lateral approach), lateral decubitus, or prone (posterior approach) depending on surgeon and access
  • Tourniquet: frequently used; pain depends on site (calf tourniquet often better tolerated than thigh tourniquet). If thigh tourniquet planned, popliteal block alone may be insufficient
    • Consider additional blocks/analgesia if thigh tourniquet or proximal incision

Anaesthetic management (typical for cases using popliteal block)

  • Type of anaesthesia: regional (popliteal sciatic) often combined with saphenous nerve block for medial ankle/foot; can be sole anaesthetic with sedation or combined with GA
    • Popliteal block covers most of foot/ankle except medial aspect (saphenous nerve, L3–4)
  • Airway: if GA required, usually SGA acceptable for short/moderate cases; ETT if prone, long duration, aspiration risk, significant comorbidity, or need for controlled ventilation
  • Duration: commonly 1–3 hours (varies widely by procedure); block duration depends on LA choice (e.g., ropivacaine/levobupivacaine 8–18+ hours analgesia)
  • How painful: moderate–severe without regional; popliteal + saphenous provides excellent postoperative analgesia; plan for tourniquet discomfort and rebound pain
    • Use multimodal analgesia and counsel about rebound pain when block wears off
  • Monitoring/standards: full AAGBI monitoring; resuscitation drugs/equipment available; intralipid immediately available for LAST

Definition and aims

  • Regional anaesthesia of the sciatic nerve in the popliteal fossa (before or after bifurcation into tibial and common peroneal nerves) to provide anaesthesia/analgesia for surgery below the knee (predominantly foot/ankle)
  • Aims: surgical anaesthesia (with/without sedation/GA), opioid-sparing analgesia, improved recovery, facilitation of day-case surgery

Indications

  • Foot and ankle surgery (excluding isolated medial foot/ankle unless combined with saphenous block)
  • Analgesia for trauma (e.g., calcaneal/ankle fractures) and postoperative pain control
  • Patients where avoidance of GA/opioids is desirable (OSA, severe PONV history, frailty) provided block is appropriate and safe

Contraindications (absolute/relative)

  • Absolute: patient refusal, allergy to LA, infection at site, inability to cooperate/consent, true compartment syndrome concern requiring serial neurovascular exams (relative/clinical judgement)
  • Relative: anticoagulation/bleeding risk (deep peripheral block near major vessels), pre-existing neuropathy, severe peripheral vascular disease, sepsis, inability to position, raised risk of nerve injury
    • Follow local policy and national guidance for deep peripheral nerve blocks in anticoagulated patients; document risk–benefit and neurological status

Relevant anatomy (exam essentials)

  • Sciatic nerve (L4–S3): divides into tibial and common peroneal nerves typically 5–10 cm proximal to popliteal crease (variable; may divide higher)
  • Popliteal fossa contents: popliteal artery and vein (deep/central), tibial nerve usually superficial and lateral to vessels; common peroneal nerve more lateral, following biceps femoris tendon
  • Sensory distribution: tibial nerve (plantar foot, heel), common peroneal (dorsum of foot via superficial peroneal; first web space via deep peroneal), sural nerve (lateral foot/ankle) arises from tibial + common peroneal contributions
  • Motor: tibial (plantar flexion, toe flexion), common peroneal (dorsiflexion/eversion). Expect foot drop until block resolves
  • Medial ankle/foot: saphenous nerve (branch of femoral) not covered by popliteal sciatic block

Approaches and technique (ultrasound-focused, with landmark options)

  • Patient position: prone (posterior approach) or supine with knee flexed/hip externally rotated (lateral approach). Choose based on comfort, access, and surgical needs
  • Ultrasound: high-frequency linear probe often sufficient; curvilinear may help in large patients/deeper nerves
  • Scanning: start at popliteal crease to identify popliteal artery/vein; identify tibial nerve superficial to vessels; track proximally until tibial and common peroneal join as sciatic (or inject around both branches if already divided)
    • Aim for circumferential spread around sciatic or around both tibial + common peroneal nerves
  • Needle: in-plane lateral-to-medial or medial-to-lateral depending on anatomy; avoid vascular structures; frequent aspiration and incremental injection
  • Nerve stimulation (optional adjunct): tibial response = plantar flexion/inversion; common peroneal response = dorsiflexion/eversion. Avoid injection with high opening pressure or pain/paraesthesia
  • Landmark (classic posterior): identify popliteal crease; needle insertion ~7–10 cm proximal in midline (or slightly lateral), advance until motor response; higher failure and vascular puncture risk vs ultrasound
  • Catheter technique: place perineural catheter adjacent to sciatic nerve for prolonged analgesia (major reconstruction, severe trauma). Secure well; educate about insensate limb and falls risk

Local anaesthetic choice and dosing (typical ranges; always individualise)

  • Volume: commonly 15–25 mL (ultrasound-guided often lower volumes effective). If injecting separately around tibial + common peroneal, split volume (e.g., 10–12 mL each) depending on spread
  • Analgesia-focused: ropivacaine 0.2–0.375% or levobupivacaine 0.25% (longer analgesia, less dense motor if lower concentration)
  • Surgical anaesthesia: ropivacaine 0.5% or levobupivacaine 0.5% (long duration; dense block). Lidocaine 1–2% gives faster onset but shorter duration
  • Adjuvants: consider per local policy (e.g., dexamethasone perineural/IV to prolong duration). Weigh off-label use, infection risk, hyperglycaemia (IV), and governance
  • Always respect maximum safe LA dose (including all blocks/infiltration). Use incremental injection, aspiration, and consider fractionated dosing with ultrasound visualisation

Block assessment and expected effects

  • Onset: 10–30 min depending on LA and concentration; assess before incision if used as sole anaesthetic
  • Sensory testing: loss of cold/pinprick on plantar foot (tibial), dorsum (superficial peroneal), first web space (deep peroneal), lateral foot (sural)
  • Motor: reduced plantar flexion and dorsiflexion; warn patient about inability to weight-bear and falls risk
  • If medial incision expected: add saphenous nerve block (adductor canal or below-knee field block at medial tibia/ankle)

Complications and management

  • Local anaesthetic systemic toxicity (LAST): risk increased with intravascular injection (popliteal vessels) and high total dose
    • Management: stop injection, call for help, airway/oxygen/ventilation, treat seizures (benzodiazepine), manage arrhythmias, give intralipid per guideline, ALS modifications (avoid large doses adrenaline; avoid lidocaine)
  • Nerve injury: intraneural injection, high pressure injection, needle trauma, ischaemia, pre-existing neuropathy; document pre-block neuro status and counsel
    • Stop if severe pain/paraesthesia on injection or high resistance; reposition needle; consider opening pressure monitoring if used locally
  • Vascular puncture/haematoma: avoid vessels with ultrasound; compress if puncture; consider anticoagulation status
  • Infection (esp. catheter): asepsis, chlorhexidine skin prep, sterile technique; remove catheter if infection suspected
  • Block failure/patchy block: high bifurcation, inadequate spread, missed saphenous territory, tourniquet pain
    • Rescue: supplement with saphenous block, distal ankle blocks, local infiltration, systemic analgesia, or convert to GA
  • Falls/pressure injury: insensate limb, motor weakness; provide crutches/boot advice; protect heel and pressure points; avoid unassisted mobilisation
  • Masking acute compartment syndrome: controversial; dense sensory block may delay diagnosis—use careful selection, low concentration where appropriate, and robust postoperative monitoring/education

Practical tips for success (FRCA-friendly)

  • Know what surgery is planned: incision sites, tourniquet level, and need for saphenous coverage
  • Aim proximal enough to catch sciatic before bifurcation if possible; if already bifurcated, deliberately block both tibial and common peroneal with visible spread
  • Use colour Doppler if unsure about vessels; popliteal vein can be compressible and easily punctured
  • Communicate expected numbness/weakness duration and safety: no driving, protect limb from heat/trauma, mobilise with assistance
Describe the sensory and motor territory of a popliteal (sciatic) nerve block. What does it NOT cover?

Core anatomy question. Examiners want clear mapping and the key omission.

  • Covers: tibial + common peroneal distributions → most of foot and ankle
    • Tibial: plantar surface, heel; motor plantar flexion/toe flexion
    • Common peroneal: dorsum of foot (superficial peroneal) + first web space (deep peroneal); motor dorsiflexion/eversion
    • Sural (often covered): lateral foot/ankle sensation
  • Does NOT cover: medial leg/ankle/foot via saphenous nerve (femoral nerve branch) → add saphenous block if medial incision
Outline how you would perform an ultrasound-guided popliteal sciatic block (step-by-step).

A common FRCA viva: structured, safe technique with ultrasound anatomy and safety checks.

  • Preparation: consent, check anticoagulation, allergies, baseline neuro exam, IV access, monitoring, intralipid available, asepsis
  • Position: prone or supine with leg externally rotated and knee flexed; ensure comfort and access
  • Scan: identify popliteal artery/vein at crease; identify tibial nerve superficial to vessels; track proximally to find sciatic before bifurcation (or identify both branches)
  • Needle: in-plane approach avoiding vessels; consider lateral-to-medial; use Doppler if needed
  • Injection: aspirate, inject incrementally with visualised spread around nerve(s); aim for circumferential spread; stop if pain/high resistance
  • Assess: sensory (cold/pinprick) and motor; document; add saphenous block if required
What local anaesthetic and volume would you choose for popliteal block for (a) analgesia only and (b) surgical anaesthesia? How do you keep it safe?

Examiners want reasonable ranges, not a single 'correct' recipe, plus safety principles.

  • Analgesia: ropivacaine 0.2–0.375% or levobupivacaine 0.25%, typically 15–25 mL (often less with ultrasound depending on spread)
  • Surgical anaesthesia: ropivacaine 0.5% or levobupivacaine 0.5% (or lidocaine for faster onset if shorter duration acceptable), volume commonly 15–25 mL
  • Safety: calculate total LA dose across all injections; incremental injection with aspiration; ultrasound visualisation; avoid intravascular injection; monitor and have LAST plan/intralipid ready
A patient has severe pain under a thigh tourniquet despite an apparently working popliteal block. Why, and what will you do?

Classic scenario: tourniquet pain and incomplete coverage.

  • Why: popliteal block anaesthetises sciatic territory below knee; thigh tourniquet pain is mediated by femoral/obturator/lateral femoral cutaneous and proximal tissues; also central sensitisation over time
  • Management options: systemic analgesia (opioids/ketamine), deepen sedation/convert to GA, consider femoral/adductor canal ± obturator/lateral femoral cutaneous blocks depending on site, or request calf tourniquet if feasible
List complications of popliteal block and how you would reduce the risk of nerve injury.

High-yield: list + prevention strategies.

  • Complications: LAST, vascular puncture/haematoma, nerve injury, infection (catheter), block failure, falls/pressure injury, potential masking of compartment syndrome
  • Reduce nerve injury: ultrasound guidance, avoid intraneural injection, stop if pain/paraesthesia or high resistance, inject incrementally, avoid deep sedation during injection, document pre-existing neuropathy, use appropriate needle and technique
How would you recognise and manage local anaesthetic systemic toxicity (LAST) during a popliteal block?

Frequently examined. Must include lipid therapy and resuscitation priorities.

  • Recognition: perioral tingling, tinnitus, metallic taste, agitation/confusion → seizures → cardiovascular collapse/arrhythmias (can be abrupt)
  • Immediate actions: stop injection, call for help, airway/100% oxygen/ventilation, treat seizures with benzodiazepine, avoid propofol in unstable patient
  • Lipid therapy: give intralipid per local/national guideline; continue supportive care and ALS modifications (small adrenaline doses; avoid lidocaine)
  • Post-event: critical care, report, document, counsel patient; consider measuring LA levels only if advised (not usually needed acutely)
The surgeon plans an incision along the medial malleolus for ankle fixation. Is a popliteal block alone sufficient? What would you add?

Tests knowledge of saphenous nerve territory.

  • Popliteal block alone is often insufficient for medial ankle/foot (saphenous nerve territory)
  • Add saphenous nerve block: adductor canal block (preferred for sensory-only) or below-knee saphenous field block at medial tibia/ankle
Where do you expect the sciatic nerve to bifurcate, and how does this affect your technique and failure rate?

Common FRCA anatomy/sono question.

  • Bifurcation is variable; often ~5–10 cm proximal to popliteal crease but can be much higher
  • Technique implication: scan proximally to find the sciatic before division; if already divided, block both tibial and common peroneal separately with adequate spread to reduce patchy block
Discuss the concern that peripheral nerve blocks may mask acute compartment syndrome (ACS). How would you manage this risk in lower limb trauma?

Regularly appears in FRCA and clinical governance discussions.

  • Risk: dense sensory block may reduce pain as a warning sign; however ACS diagnosis is clinical and multifactorial (pain out of proportion, pain on passive stretch, tense compartments, neurovascular changes, pressure measurement)
  • Mitigation: careful patient selection; discuss with surgical team; consider using lower concentration for analgesia rather than dense surgical block; ensure robust postoperative monitoring and clear escalation plan; document discussion and neurovascular baseline

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