Author(s): Chrissa McClellan, MD, PT, Andrew Goldblum, DO, Benjamin Boyett, MD
Originally published: August 30, 2013 Last updated: July 10, 2025
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Disease/Disorder

Definition

Mononeuropathies of the distal lower extremity (lower leg, ankle and foot) include the proximal tibial nerve, common fibular (peroneal) nerve with deep and superficial branches, and the sural nerve with contributions from both tibial and fibular nerves. Mononeuropathies of the distal tibial nerve, passing through the posterior tarsal tunnel, are addressed under the article titled Tarsal Tunnel Syndrome. The saphenous nerve branch of the femoral nerve supplies some distal sensory innervation and is addressed under the article titled Proximal Mononeuropathies of the Lower Extremity.

Etiology

Mononeuropathies occur in many ways including:

  • Entrapment: in a fascial layer or a fibrous tunnel (conditions causing soft tissue component enlargement, overgrowth, edema or inflammation such as tumor, pitting edema from fluid overload, myxedema in hypothyroidism, rheumatoid arthritis, osteoarthritis)1,2
  • Internal compression: Bone spurs, bursitis,3 nerve tumors, masses such as ganglion cyst4
  • External compression/ Biomechanics: external factors from braces, compressive clothing or tight foot wear4 recurrent ankle sprains or foot/ankle positioning against firm surfaces5
  • Iatrogenic injury during medical or surgical procedures6
  • Compartment syndrome from fluid shifts7

Epidemiology including risk factors and primary prevention

Though nerve entrapment of the lower leg ankle and foot is rather uncommon3, the most common mononeuropathy of the lower extremity is common fibular at the fibular head.4,8Prevention includes proper positioning of prolonged bed rest patients and avoiding external compression from various sources including medical devices such as braces and casts.

Patho-anatomy/physiology

Common fibular (peroneal) nerve

NerveNerve RootsNerve CourseSensory & Motor InnervationSites of Injury and Etiology
Common fibularL4-S29,10Fibular division of sciatic nerve around fibular head through a fibro-osseous tunnel, gives a branch to the sural nerve, and divides into the deep and superficial branches9,10Sensory: anterior shin, dorsum foot and first web space10

Motor: ankle dorsiflexors and everters10		Fibular head: external compression from habitual leg crossing, significant weight loss (slimmer’s palsy),2,11,12 prolonged immobilization,2,4 repetitive squatting (strawberry picker’s palsy),2 intraneural ganglion cyst,2,4,10,13 trauma,2,4,10 tight cases/orthoses,10 repetitive ankle inversion injuries10
Deep fibular Branches from common fibular nerve at the fibular head and courses anteriorly into the deep anterior compartment of the leg across the ankle under the superior and inferior extensor retinaculum9,10Sensory: First web space9,14

Motor: Tibialis anterior, extensor hallucis longus, peroneus tertius, extensor digitorum longus, extensor digitorum brevis9,14		Anterior tarsal tunnel syndrome: ankle instability/trauma,3 talonavicular joint osteophytes,3 entrapment under the inferior extensor retinaculum,10 space occupying lesions, extreme plantarflexion in dancing,10 tight fitting shoes5,10

Anterior compartment syndrome: due to chronic exertional activities or trauma10  
Superficial fibular Courses through the lateral compartment of the lower leg3 pierces the deep fascia, then passes anterior to the ankle (superficial to the extensor retinaculum)9,10Sensory: Lateral calf, dorsum of foot9,14

Motor: Peroneus longus and brevis9,14		Entrapment due to a thickened deep fascial tunnel,3 traction injury due to repeat lateral ankle sprains,3,10 compression at the ankle from tight shoes (“ski boot neuropathy”)4,10
Proximal TibialL4-S39,10Tibial division of the sciatic nerve courses through the popliteal fossa and into the posterior leg and around the medial malleolus (under the flexor retinaculum) through the tarsal tunnel, branches into calcaneal,  medial and lateral plantar branches9,14Sensory: Posterior calf, plantar aspect of foot9

Motor: Soleus, Tibialis Posterior, Gastrocnemius, flexor digitorum longus, flexor hallucis longus, intrinsic muscles of the foot9,14		Popliteal mass, Baker’s cyst, iatrogenic (total knee replacements), entrapment under fibrous band of soleus muscle (soleal sling syndrome).3 For distal tibial neuropathy, see article titled “Tarsal Tunnel Syndrome.”
SuralS1-29Branches of the tibial and common fibular nerve near the popliteal fossa, courses superficial posterior leg around the lateral malleolus9Sensory: Posterior leg, lateral ankle and foot9

Motor: None		Recurrent ankle sprains, tight shoes, iatrogenic (biopsy, Achilles repair or ankle arthroscopy), trauma, space occupying lesions (ganglion cysts)3,10,15

Specific secondary or associated conditions and complications

Ankle contractures from severe foot drop can develop. Complex regional pain syndrome may be a sequela of nerve injury. Falls due to poor foot clearance may occur. Severe sensory loss can predispose to skin breakdown, particularly in patients with preexisting peripheral neuropathy.

Essentials of Assessment

Detailed, precise history and physical examination and judicious use of electrodiagnostic and imaging modalities (such as MRI and ultrasonography) will help to determine the location and severity of the mononeuropathy.1

History

History for mononeuropathies of the leg may include antecedent injury, trauma, medical condition, or surgery. Habitual positions or repetitive motions may be pertinent. Occupational and avocational activities (hobbies, sports such as long-distance running) and associated shoe wear may be a causative or contributing factor. The patient may present with paresthesia (in distribution of affected nerve), pain (at rest, at night, during or after exertion)and/or muscle weakness.5

Physical examination

NerveSensoryMotorSpecial Testing/Other
Common fibularSensory loss over lateral leg, dorsum foot and first web space4Weakness of foot dorsiflexion and eversion4Steppage gait Positive Tinel’s at the fibular head4,10
Deep fibularSensory loss of first web space4Weakness of dorsiflexion4 and toe extensionAtrophy of EDB
Superficial fibularSensory loss dorsum of foot, pain lateral leg4,10Weakness of eversion4Nerve percussion lateral leg/anterior ankle, muscle herniation in lateral leg10
Proximal TibialSensory loss dorsum of foot9Weakness of foot plantar flexion (heel raises)Calf atrophy
SuralDistal calf and lateral ankle pain and paresthesias,10 sensory loss posterior calf and lateral foot9None, sensory nerve onlyPositive percussion, provocative ankle inversion10

Imaging

NMUS can be used for evaluation of the fibular nerve as it traverses around the fibular head, a common site for compression. This technique allows for visualization and measurement of the nerve’s cross-sectional area (CSA) and side to side comparisons. An increased CSA, as well as an elevated ratio of the CSA of the fibular nerve at the fibular head to the popliteal fossa, are both associated with fibular neuropathy and foot drop.16 Additionally, NMUS can be used for the detection of other pathologies both intrinsic and extrinsic to the nerve that can cause fibular neuropathy. This includes but is not limited to ganglion cysts, synovial cysts, vascular aneurysms, fabellar compression, osteochondromas, and nerve sheath tumors. The most common of these identified causes of compression are ganglion cysts.13, 14

Supplemental assessment tools

Electrodiagnostic studies identify and confirms the level, degree, age and prognosis of nerve injury and should include nerve conduction studies and EMG to rule out proximal injuries such as lumbosacral plexopathies, radiculopathies of the L5 or S1 root levels, or sciatic nerve injuries.4,10,13

NeuropathySensory NCS Findings4,13,14Motor NCS Findings4,13,14  EMG Findings4,13,14
Common fibular    Demyelinating      

Axonal		Normal superficial fibular SNAP

↓ superficial fibular and sural SNAP amplitudes		Fibular CMAP to EDB and TA: ↓ CV across and/or CB across the fib head

↓ CV across the fib head and ↓ fibular CMAP amplitudes to EDB and TA		May or may not have ↓ recruitment TA, PL, EHL (normal Biceps SH)

Fibs/PSW in TA, PL, EHL (normal Biceps SH)    
Deep fibular at the ankleNormal superficial fibular SNAP↓ fibular CMAP amplitudes to EDB; normal fibular CMAP to TAFibs/PSW in EDB, with normal EMG to TA, PL, EHL
Superficial fibular at the ankle↓ superficial fibular SNAP amplitudesNormal fibular CMAP to EDB and TANormal EMG to TA, PL, EDB, EHL
Proximal tibial↓ sural SNAP amplitudes↓ tibial CMAP amplitudes to AHFibs/PSW in Gastroc, Soleus, PT, FDL depending on the location of lesion
Sural↓ sural SNAP amplitudesNormal tibial CMAP to AHNormal

SNAP: sensory nerve action potential; CMAP: compound motor action potential; CV: conduction velocity; CB: conduction block; EDB: extensor digitorum brevis; TA: tibialis anterior; AH: abductor hallucis; PL: peroneus longus; EHL: extensor hallucis longus; SH: short head; Fibs: fibrillations; PSW: positive sharp waves; PT: posterior tibialis; FDL: flexor digitorum longus

Rehabilitation Management and Treatments

Available or current treatment guidelines

Treatment is aimed at prevention, managing symptoms and addressing any resulting impairments.

  • Prevention/Alleviate compression: Modification of pain-inducing or compression activities 12 such as avoidance of squatting and leg crossing, proper positioning of bedridden patients, modification of casts or orthoses, shock absorbing shoe inserts, shoe modifications, education on possible risks associated with weight loss, running techniques modification10,11
  • ankle foot orthoses (AFO)11for foot drop in fibular nerve injuries and orthoses for calf weakness in tibial nerve injury may be helpful.2
  • Physical therapy: strengthening, range of motion to prevent or address contracture, muscle stretching to help maintain muscle for future reinnervation and effective function, gait retraining, physical modalities, e.g. TENS, soft tissue manipulation and cryotherapyfor pain management.5,15
  • Pharmacology: Topical and oral pharmacologic agents, such as non-steroidal anti-inflammatories (NSAID) and neuropathic pain management including gabapentin, pregabalin, GABA analog, tricyclic antidepressants.3
  • Ultrasound-guided injection: If conservative treatment fails and an entrapment site is located, an ultrasound guided nerve block can be performed to obtain additional diagnostic information.5,10 and hydro dissection may provide symptomatic relief.11
  • Surgical intervention: Early surgical intervention is appropriate during urgency and emergency situations such as nerve transection (nerve repair), acute compartment syndrome (fasciotomy), and space-occupying lesions with progressive neurologic deficit (resection of mass). If conservative measures fail, neurolysis with or without fascial release can be considered.3,5,10,11

Coordination of care

Physical and occupational therapy can address exercise, avocational and occupational needs. The orthotist can evaluate and modify braces or shoe wear. The electromyographer can guide surgical exploration and treatment. Communication with nursing staff and caregivers is important to ensure proper positioning for patients on bed rest.

Patient & family education

Patients and caregivers should be educated on avoidance of exacerbating activities, positioning, daily skin care and precautions for insensate foot

Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

EMG is extremely useful in localizing nerve lesion, assessing for signs of reinnervation, determining severity, prognosis for recovery, and ruling out alternative diagnoses.4,14 Neuromuscular ultrasound, now widely used in physiatry, is very helpful in determining structural abnormalities that may be contributing to the neuropathy, for which electrodiagnostics cannot determine.13

Cutting Edge/Emerging and Unique Concepts and Practice

With the introduction of GLP-1 medications and significant weight loss, patients may be more susceptible to slimmer’s palsy (common fibular neuropathy).12

Neuromuscular ultrasound is being utilized more frequently in common fibular neuropathy to look for structural causes.

Microsurgical decompression of common fibular nerve entrapment under local anesthesia in a study on 22 patients showed good postoperative symptom relief on a follow-up period of 40 months.11

Peripheral nerve stimulator (PNS) placement for the superficial fibular, sural and tibial nerves has been reported to give pain relief utilizing ultrasound guided percutaneous leads implanted in the superficial fibular nerve in the distal leg11,17

Gaps in the Evidence-Based Knowledge

Additional large randomized clinical trials comparing the outcomes of new surgical techniques and peripheral nerve stimulation is needed to assess for efficacy.

References

  1. Madani S, Doughty C. Lower extremity entrapment neuropathies. Best Pract Res Clin Rheumatol. 2020;34(3):101565. doi:10.1016/j.berh.2020.101565
  2. Bowley MP, Doughty CT. Entrapment Neuropathies of the Lower Extremity. Med Clin North Am. 2019;103(2):371-382. doi:10.1016/j.mcna.2018.10.013
  3. Pomeroy G, Wilton J, Anthony S. Entrapment Neuropathy About the Foot and Ankle: An Update. JAAOS – J Am Acad Orthop Surg. 2015;23(1):58. doi:10.5435/JAAOS-23-01-58
  4. Electromyography and Neuromuscular Disorders.; 2020. Accessed April 3, 2025. https://shop.elsevier.com/books/electromyography-and-neuromuscular-disorders/preston/978-0-323-66180-5
  5. Ferkel E, Davis WH, Ellington JK. Entrapment Neuropathies of the Foot and Ankle. Clin Sports Med. 2015;34(4):791-801. doi:10.1016/j.csm.2015.06.002
  6. Puijk R, Rassir R, Kok LM, Sierevelt IN, Nolte PA. Common peroneal nerve palsy after TKA in valgus deformities; a systematic review. J Exp Orthop. 2022;9(1):12. doi:10.1186/s40634-021-00443-x
  7. Rajasekaran S, Finnoff JT. Exertional Leg Pain. Phys Med Rehabil Clin N Am. 2016;27(1):91-119. doi:10.1016/j.pmr.2015.08.012
  8. Fortier LM, Markel M, Thomas BG, Sherman WF, Thomas BH, Kaye AD. An Update on Peroneal Nerve Entrapment and Neuropathy. Orthop Rev. 13(2):24937. doi:10.52965/001c.24937
  9. Atlas of Human Anatomy Professional Edition 7th Edition – Netter Reference. Accessed April 3, 2025. https://netterreference.com/index.php/bookshelf/41
  10. Meadows JR, Finnoff JT. Lower extremity nerve entrapments in athletes. Curr Sports Med Rep. 2014;13(5):299-306. doi:10.1249/JSR.0000000000000083
  11. Fortier LM, Markel M, Thomas BG, Sherman WF, Thomas BH, Kaye AD. An Update on Peroneal Nerve Entrapment and Neuropathy. Orthop Rev. 13(2):24937. doi:10.52965/001c.24937
  12. Pennington N. Slimmer’s Paralysis: A Case Study of Peroneal Neuropathy Following Rapid Weight Loss. J Nurse Pract. 2024;20(8). doi:10.1016/j.nurpra.2024.105117
  13. Ultrasound Evaluation of Peripheral Nerves and Focal Neuropathies, Second Edition (Hardcover) by Jeffrey A. Strakowski: new Hardcover (2020) | Grand Eagle Retail. Accessed April 17, 2025. https://www.abebooks.co.uk/Ultrasound-Evaluation-Peripheral-Nerves-Focal-Neuropathies/30804372309/bd
  14. Fridman V, David WS. Electrodiagnostic Evaluation of Lower Extremity Mononeuropathies. Neurol Clin. 2012;30(2):505-528. doi:10.1016/j.ncl.2011.12.004
  15. Flanigan RM, DiGiovanni BF. Peripheral nerve entrapments of the lower leg, ankle, and foot. Foot Ankle Clin. 2011;16(2):255-274. doi:10.1016/j.fcl.2011.01.006
  16. Bucklan JN, Morren JA, Shook SJ. Ultrasound in the diagnosis and management of fibular mononeuropathy. Muscle Nerve. 2019;60(5):544-548. doi:10.1002/mus.26652
  17. Hanyu-Deutmeyer A, Pritzlaff SG. Peripheral Nerve Stimulation for the 21st Century: Sural, Superficial Peroneal, and Tibial Nerves. Pain Med. 2020;21(Supplement_1):S64-S67. doi:10.1093/pm/pnaa202

Original Version of the Topic

Anita S.W. Craig, DO. Distal lower extremity mononeuropathies. 8/30/2013.

Previous Revision(s) of the Topic

Poonam Ochani, MD. Distal lower extremity mononeuropathies. 7/31/2017.

Poonam Ochani, MD. Distal Lower Extremity Mononeuropathies. 5/19/2022.

Author Disclosure

Chrissa McClellan, MD, PT
Nothing to Disclose

Andrew Goldblum, DO
Nothing to Disclose

Benjamin Boyett, MD
Nothing to Disclose