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lateral popliteal nerve palsy

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The common peroneal nerve represents a major nerve terminal of the sciatic nerve

  • the nerve is divided into two main branches when it pierces the peroneus longus muscle to reach the anterior compartment of the lower leg
    • deep peroneal nerve
      • supplies the muscles that control foot dorsiflexion and toe extension (tibialis anterior, extensor digitorum longus, peroneus tertius, and extensor hallucis longus)
        • tibialis anterior is the strongest contributor to foot dorsiflexion while , extensor digitorum longus, peroneus tertius also assist
      • in the foot it supplies the short toe extensors, the extensor digitorum brevis, and extensor hallucis brevis. sensory branch supplies the interspace between the first and second toes
    • superficial peroneal nerve 
      • supplies  the peroneus longus and brevis
      • supplies sensation to the skin of the lateral leg and the dorsum of the foot and toes (sparing the small area between the first two toes and a variable lateral part of the foot) (1,2)

Clinical features include:

  • foot drop
  • weakness of dorsiflexion and eversion of the foot
  • weakness of extensor hallucis longus
  • inversion and plantar flexion are normal
  • anaesthesia over the lower lateral part of the leg and dorsum of the foot; often with little or no sensory loss
  • all reflexes are intact - the ankle jerk is lost in a sciatic nerve lesion
  • wasting of the anterior tibial and peroneal muscles

Recovery occurs within a few weeks when the cause is simple compression. Full knee flexion should be avoided as in kneeling or squatting, and the patient should not sit with the legs crossed over the unaffected leg. To prevent foot drop the patient should wear an aluminium night-shoe at night and during the day, a shoe with plastic inserts.

Surgical exploration is indicated if the weakness progresses or fails to resolve within 1-2 months, or if there is an obvious local lesion.