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Saphenous Nerve Entrapment

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Other Names

  • Saphenous Neuropathy
  • Surfer's neuropathy
  • Entrapment Neuropathy of the Infrapatellar Branch of the Saphenous Nerve
  • Infrapatellar Saphenous Neuralgia
  • Saphenous neuroma
  • Saphenous neuropathic pain syndrome
  • Gonalgia Paresthetica

Background

History

Epidemiology

  • Incidence is not well documented in the literature

Pathophysiology

Saphenous nerve anatomy at the medial knee. Note the relationship of sartorius to the infrapatellar branch (IPS nerve) and the saphenous nerve[1]
  • Misdiagnosis
    • Easily missed and overlooked by physicians
    • Often misdiagnosed as more common causes of medial knee pain (meniscus, MCL, PFPS, knee OA, pes anserine pain)
    • Often fail other common treatment modalities due to misdaignosis

Etiology

  • Entrapment at the medial knee[2]
    • Courses deep to Sartorius traveling laterally to medially as it descends the thigh
    • Nerve exits through adductor (Hunter's) canal at medial knee, then travels distally into the calf
  • Iatrogenic during orthopedic surgery
  • Other causes
    • Prolonged periods of kneeling
  • Case reports following
    • Blunt trauma to medial thigh[8]

Pathoanatomy

  • Saphenous Nerve
    • Sensory branch of the Femoral Nerve
    • Distribution is medial leg
    • Medial femoral condyle: divides into infrapatellar branch, terminal saphenous branch
  • Infrapatellar branch: innervates the skin below the patella, anterior inferior knee capsule
  • Terminal saphenous branch: innervates the skin of the anterior and medial lower leg

Risk Factors

  • Sports
    • Surfing

Differential Diagnosis

Clinical Features

  • History
    • The patient will complain of vague medial knee pain
    • Can radiate down medial aspect of leg into the foot
    • Pain may or may not be worse with movement
    • Pain may be described as dull, achy, burning
    • Worse with stairs, sitting, prolonged walking[9]
  • Physical Exam: Physical Exam Knee
    • Medial tibial fossa may demonstrate swelling
    • May be tender over medial tibial plateau or fossa, medial patellar facet, retinaculum
    • Diminished sensation to light touch of anteromedial knee
    • Hypesthesia or allodynia may be present
    • Knee flexion and abduction may increase pain and give false positive to meniscus etiology
  • Special Tests
    • Tinels Test: percussion over the adductor canal or medial tibial fossa may replicate pain
      • Adductor canal: approximately 7 cm proximal, 10 cm medial to superior pole of patella
      • Infrapatellar branch: 3-5 cm medial to the medial mid-patella border with knee in extension

Evaluation

Demonstration of diagnostic injection for infrapatellar branch[1]

Radiographs

EMG/NCS

  • Described in literature
  • Questionable utility
    • Likely less valuable than a diagnostic injection

Diagnostic Nerve Block

  • Description for infrapatellar branch
    • Knee is in flexion
    • Isolate the point of maximal tenderness in the medial tibial fossa
    • Needle enters from below, directed towards tibial tubercle and advanced to bone
    • Consider adding corticosteroid to injection
    • Use small volumes (1-2 mL) to avoid local anesthetic infiltrating other areas and avoiding confounding
  • Consider using ultrasound guidance

Classification

  • Not applicable

Management

Nonoperative

Procedures

Operative

  • Indications
    • Failure of conservative measures
  • Technique
    • Surgical decompression[12]
    • Neurolysis
    • Neurectomy

Rehab and Return to Play

Rehabilitation

  • Needs to be updated

Return to Play/ Work

  • Needs to be updated

Complications and Prognosis

Prognosis

  • Unknown

Complications

  • Chronic knee pain

See Also

References

  1. ↑ 1.0 1.1 Trescot, Andrea M., Michael N. Brown, and Helen W. Karl. "Infrapatellar saphenous neuralgia-diagnosis and treatment." Pain physician 16.3 (2013): E315-24.
  2. ↑ Kalenak, Alexander. "Saphenous nerve entrapment." Operative Techniques in Sports Medicine 4.1 (1996): 40-45.
  3. ↑ Dellon AL, Mont MA, Krackow KA, Hungerford DS. Partial denervation for persistent neuroma pain after total knee arthroplasty. Clin Orthop Relat Res 1995; 316:145-150.
  4. ↑ Papastergiou SG, Voulgaropoulos H, Mikalef P, Ziogas E, Pappis G, Giannakopoulos I. Injuries to the infrapatellar branch(es) of the saphenous nerve in anterior cruciate ligament reconstruction with four-strand hamstring tendon autograft: Vertical versus horizontal incision for harvest. Knee Surg Sports Traumatol Arthrosc 2006; 14:789-793.
  5. ↑ Kartus J, Movin T, Karlsson J. Donor-site morbidity and anterior knee problems after anterior cruciate ligament reconstruction using autografts. Arthroscopy 2001; 17:971-980
  6. ↑ Mochida H, Kikuchi S. Injury to infrapatellar branch of saphenous nerve in arthroscopic knee surgery. Clin Orthop Relat Res Nov 1995; 320:88-94.
  7. ↑ Leliveld MS, Verhofstad MHJ. Injury to the infrapatellar branch of the saphenous nerve, a possible cause for anterior knee pain after tibial nailing? Injury 2012; 43:779-783.
  8. ↑ Herman, Daniel C., and Kevin R. Vincent. "Saphenous neuropathy—a masquerading cause of anteromedial knee pain." Current sports medicine reports 17.6 (2018): 177.
  9. ↑ Morganti CM, McFarland EG, Cosgarea AJ. Saphenous neuritis: a poorly understood cause of medial knee pain. J. Am. Acad. Orthop. Surg. 2002; 10:130–7.
  10. ↑ Akbas M, Luleci N, Dere K, Luleci E, Ozdemir U, Toman H. Efficacy of pulsed radiofrequency treatment on the saphenous nerve in patients with chronic knee pain. J Back Musculoskelet Rehabil 2011; 24:77-82.
  11. ↑ Trescot A. Cryoanalgesia in interventional pain management. Pain Physician 2003; 6:345-360.
  12. ↑ Lippitt, A. B. "Neuropathy of the saphenous nerve as a cause of knee pain." Bulletin (Hospital for Joint Diseases (New York, NY)) 52.2 (1993): 31-33.
Created by:
John Kiel on 15 August 2021 22:10:24
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Last edited:
4 October 2022 15:56:10
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