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The lower abdominal wall, hip, thigh and knee are affected by neuropathies of the iliohypogastric, ilioinguinal, genitofemoral, femoral, obturator, and lateral femoral cutaneous nerves.

Etiology, Epidemiology including risk factors and primary prevention

Nerve Etiology, epidemiology, risk factors
Ilioinguinal, iliohypogastric, genitofemoral Iatrogenic mechanical injury during surgery: appendectomy, hysterectomy, inguinal hernia repair, and cesarean delivery.

–          Risk with gynecologic surgery about 2%.1,2

–          Risk for ilioinguinal and iliohypogastric neuropathic pain after laparoscopic incision in the lower abdomen about 5%.3

–          Postoperative risk of inguinodynia after inguinal hernioplasty with mesh about 10%.4


Blunt abdominal trauma and visceral adhesions.


Constrictive clothing around the abdomen.5

Femoral Iatrogenic mechanical injury during surgery: approximately 0.1 – 0.2% of total hip arthroplasties complicated by femoral nerve injury.6 Increased risk associated with anterior or anterolateral approach, self-retaining retractors and lithotomy position.

Increased risk during pelvic surgery with thin body habitus and dorsal lithotomy position.7
Femoral catheterization procedures.8
Retroperitoneal hematoma.8

Lateral femoral cutaneous Iatrogenic mechanical injury during surgical procedures such as hernia repair, renal transplant, iliac bone graft harvesting, hip surgery and femoral catheterization procedures.


External compression: from heavy tool belts, tight waistbands or seat belts.
Internal compression: from aortic aneurysm or pelvic masses.


Risk factors include obesity, pregnancy, diabetes, rapid weight loss.9

Obturator Iatrogenic mechanical injury during surgical procedures such as total hip arthroplasty, pelvic operations.


Rarely injured in isolation, but often in the setting of other nerve or plexus injuries with pelvic trauma or sacroiliac joint disruption.
Increased risk with lithotomy position.8


Nerve Nerve roots Nerve course Cutaneous innervation Motor innervation Common injury location
Ilioinguinal L1 (variable T12) Travels along the lateral border of psoas, along the iliac crest, pierces transversus abdominus near the  anterior superior iliac spine (ASIS). Travels with the spermatic cord/round ligament in the inguinal canal. Proximal inner thigh

Base of penis

Upper scrotum

Mons pubis

Lateral labia

Internal oblique Psoas muscle, transversus abdominis muscle, and inguinal canal
Iliohypogastric L1 (variable T12) Travels along the lateral border of psoas

The lateral cutaneous branch penetrates the internal and external oblique muscles above the iliac crest.

The anterior cutaneous branch passes along the crest of the ilium, enters the internal oblique muscle at the level of the ASIS and runs through the aponeurosis of the external oblique muscle.

Lateral cutaneous branch supplies the skin of the gluteal region

Anterior cutaneous branch supplies the abdominal skin at the inguinal ligament

Internal oblique Psoas muscle, and transversus abdominis muscle
Genitofemoral L1-2 Pierces the psoas

The femoral branch passes under the inguinal ligament.

The genital branch passes through the inguinal ligament.

Proximal medial thigh

Labia majora

Distal scrotum

Cremasteric muscle (males) Psoas muscle, transversus abdominis muscle, inguinal ligament
Femoral L2-L4 Descends through the psoas muscle, passes in a groove between the psoas and iliacus. After sending motor branches to psoas and iliacus, passes under the inguinal ligament and divides into four terminal branches. Anterior thigh

Anterior patella, medial leg. Medial ankle via saphenous nerve



Quadriceps (vastus medialis, intermedius and lateralis; rectus femoris)



Anterior surface of psoas

Under the inguinal ligament

Lateral femoral cutaneous L2-3 Exits the pelvis close to the ASIS and inguinal ligament Anterolateral thigh Under the inguinal ligament near the ASIS9
Obturator L2-4 Forms within the psoas muscle, runs anterior to the sacroiliac (SI) joint. Passes between the obturator muscles and the obturator sulcus of the pubic bone. Distal ⅔ of medial thigh Adductor brevis and longus; obturator externus, gracilis, and portion of adductor magnus (with sciatic nerve). Variably innervates pectineus Entrapment in fascia overlying the adductor brevis or in the adductor compartment in athletes8

 Specific secondary or associated conditions and complications

Proximal muscle weakness can cause instability around the hip and knee, resulting in falls. Progression of mobility after a trauma may be delayed because of unrecognized neurologic lesions. Protective postures because of neuropathic pain may lead to hip flexion contractures. Complex regional pain syndrome may develop.



Patients often present with an acute pelvic fracture, blunt trauma around the ASIS or groin or after inguinal herniorrhaphy, hip surgery, pelvic surgery, or vascular catheterization. Injury may not initially be identified because of acute injury or surgery. Patients present with numbness or weakness in the anatomic nerve distribution.

Patients with meralgia paresthetica present with numbness, parethesias and pain in the lateral aspect of the thigh as a result of damage to the lateral femoral cutaneous nerve.

Physical examination

Generally, mononeuropathies of these nerves will result in pain or abnormal sensation in the cutaneous distributions listed above. Other physical exam findings are as follows:

Nerve Strength disturbance Special physical exam considerations
Ilioinguinal, Iliohypogastric, Genitofemoral Genitofemoral lesion affects cremasteric reflex. Patients may adopt a forward flexed posture as lumbar extension stretches the nerves.

Weakness of the anterior abdominal muscle can contribute to hernia formation.

Femoral Hip flexion and knee extension weakness if injured in the pelvis. Isolated knee extension weakness if injured distal to the inguinal ligament. Patellar reflex can be hypoactive.

Hip extension can be painful.

Patients may feel the ipsilateral knee is unstable or buckling.

Lateral femoral cutaneous No strength disturbances should be observed. Pain or sensory disturbances in the anterolateral thigh may be exacerbated by walking, hip extension or compressive garments.

May have a positive Tinel’s sign medial and inferior to the ASIS.8

Obturator Hip abduction and internal rotation weakness. Pain induced by exercise with entrapment in the adductor canal.8

Sensory disturbance in the medial thigh

Functional assessment

Pain from traumatic injury, such as fractures and orthopedic restrictions, may initially mask nerve injury symptoms. As recovery ensues, symptoms become apparent. A persistent forward-flexed posture may be observed because of pain from neural tension. Internal hip rotator weakness may cause extremity to externally rotate during ambulation and cause a circumducted gait. Femoral and obturator weakness interferes with transfers, such as lifting the limb in and out with bed, bathtub, and stair use.


Plain radiographs should be obtained in traumatic injury to assess for fractures of the pelvis or proximal femur, to detect bony exostosis, heterotopic ossification, or tumor that impinges on the course of the nerves. Computerized tomography can show bony lesions in greater detail. Magnetic resonance imaging provides detailed visualization of anatomic structures, such as tumor and hematoma, along with direct visualization of nerves and signal change associated with denervated muscle or nerve injury.[1]0 Ultrasonography can visualize nerves and help localize injury location. An injured lateral femoral cutaneous nerve will show significantly larger diameter on ultrasound than on the asymptomatic side.11

Considerations in MRI and US evaluation:

Nerve Ultrasound MRI
Ilioinguinal Iliohypogastric


Ilioinguinal nerve is best visualized immediately medial to the ASIS.

The iliohypogastric can typically be found within 1 cm of the ilioinguinal nerve at this point.12

The genital branch of the genitofemoral nerve is a common target for injection but generally cannot be seen without a high frequency probe (> 18 Hz).13

Femoral Evaluation of the intrapelvic portion is difficult owing to its deep position and interference from bowel gas.

The mean cross-sectional area in the infrainguinal region is 22.7 mm2 but it divides into multiple branches < 1 mm2 within 3-4 cm distal to the inguinal ligament.14

Detection of the intrapelvic portion may be difficult given its oblique path and close proximity to the iliacus muscle.
Lateral femoral cutaneous The nerve can be found on the surface of the sartorius and traced back to the inguinal ligament.

Fusiform nerve swelling can be seen between the deep circumflex iliac artery and inguinal ligament with nerve flattening under or within the inguinal ligament in meralgia paresthetica.15,16

A sonographic Tinel’s sign may be present at the site of injury.

Focal increased T2 signal intensity in the proximity of the inguinal ligament can be seen in meralgia paresthetica.17
Obturator May be seen distally in the fat planes between the pectineus and adductor longus and along the anterior and posterior aspect of the adductor brevis muscles. May coexist with adductor tendinopathy. Signal change in medial thigh muscles may be seen with denervation injury.


Supplemental assessment tools

Electrodiagnostic testing is very useful in identifying the lesion, localizing level of injury, assessing the severity and chronicity, and is critical in evaluating plexus or root lesions in trauma or iatrogenic injury.

Nerve Nerve Conduction Study (NCS) Electromyography (EMG) Normative studies
Ilioinguinal, iliohypogastric, genitofemoral None Ilioinguinal: denervation in lower abdominal muscles Exclude lumbar radiculopathy or upper plexus lesion with proximal thigh and paraspinal muscle EMG
Femoral Technically challenging due to the depth of the nerve

Compare with unaffected side

Saphenous studies should be compared to unaffected side

Iliopsoas and quadriceps muscles help localize the lesion in relation to the inguinal ligament.

EMG will be normal in isolated saphenous nerve injuries.

A compound action potential amplitude of at least 50% of the other side, obtained between 10 days to a month after injury, predicts good prognosis for recovery within 1 year.10,15

Lateral femoral cutaneous Technically challenging

Compare with unaffected side.


The use of ultrasound to localize the nerve can improve the ability to record a response.9,18

None Thigh and L3-L5 innervated muscles
Obturator None Denervation in adductor longus

Possible denervation in adductor magnus (partially sciatic innervated)

Professional Issues

Iatrogenic injury to proximal nerves is very common in many pelvic and orthopedic procedures. Patients can be reassured that in most cases good recovery can be expected. Discussion of the possibility of such injuries should be part of routine discussion of operative risks. Recurrent injuries, however, warrant examination of intraoperative procedures, particularly in the employment of self-retaining retractors and patient positioning.


Available or current treatment guidelines

Treatment depends on etiology:

  • Compressive lesion from tumor/mass: surgical decompression. Hematoma may require correction of anticoagulation and urgent drainage. Correction of hernias can relieve compression.
  • If painful, medications, such as tricyclic antidepressants, anticonvulsants, and topical agents, such as lidocaine and capsaicin, can be prescribed. Transcutaneous electrical nerve stimulation or acupuncture may be useful.
  • Nerve blocks can be diagnostic and therapeutic.18
  • Surgical exploration and neurolysis should be considered if there is no improvement after 3 to 6 months of conservative management.8,19
  • A knee-ankle-foot orthosis, when quadriceps weakness is severe, with a few degrees of ankle plantar flexion can assist the extension moment at the knee.
  • To compensate for quadriceps weakness, the patient can be trained to activate the gluteus maximus, hamstring muscles, and the gastroc-soleus muscles during stance phase to assist knee extension.

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

  • When assessing a patient with a traumatic injury to the pelvis, keep a high index of suspicion for neurologic injury, particularly because such injuries can easily be masked by pain, orthopedic restrictions, and altered mental status or sedation.
  • Likewise, in patients who have had lower abdominal or pelvic surgeries, any unexpected pain, weakness, or delay in progress should raise suspicion for nerve damage.
  • EMG can aid in differentiating neurologic injury from deficits because of orthopedic injury. It can also assist in localizing the level of the lesion, severity, and prognosis.


Computed tomography (CT)-guided diagnostic and therapeutic perineural injections are becoming increasingly common for chronic pelvic pain.20


Imaging of peripheral nerves around the hip and pelvis is challenging due to their small size, variable course and the complexity of the associated anatomy. Additionally, electrophysiologic studies are challenging due to the depth of the nerves and their complex and variable courses. Ultrasound and magnetic resonance imaging (MRI) are currently used to visualize these nerves but the results are very operator dependent.


  1. Bohrer, J., Walters, M., Park, A., Polston, D., & Barber, M. (2009). Pelvic nerve injury following gynecologic surgery: A prospective cohort study. American Journal of Obstetrics and Gynecology., 201(5), 531.e1-531.e7.
  2. Cardosi, R., Cox, C., & Hoffman, M. (n.d.). Postoperative neuropathies after major pelvic surgery. Obstetrics and Gynecology., 100(2), 240-244.
  3. Shin, J., & Howard, F. (n.d.). Abdominal wall nerve injury during laparoscopic gynecologic surgery: Incidence, risk factors, and treatment outcomes. Journal of Minimally Invasive Gynecology., 19(4), 448-453.
  4. Zannoni, M., Luzietti, E., Viani, L., Nisi, P., Caramatti, C., & Sianesi. (n.d.). Wide resection of inguinal nerves versus simple section to prevent postoperative pain after prosthetic inguinal hernioplasty: Our experience. World Journal of Surgery., 38(5), 1037-1043.
  5. Elkins, N., Hunt, J., & Scott, K. (n.d.). Neurogenic Pelvic Pain. Physical Medicine and Rehabilitation Clinics of North America., 28(3), 551-569.
  6. Yang, I. (n.d.). Neurovascular Injury in Hip Arthroplasty. Hip & Pelvis, 26(2), 74-78.
  7. Clarke-Pearson, D., & Geller, E. (n.d.). Complications of hysterectomy. Obstetrics and Gynecology., 121(3), 654-673.
  8. Craig, A., Richardson, J., & Ayyangar, R. Braddom’s Physical Medicine and Rehabilitation, Published January 1, 2016. Chapter 41, 907-942.e4
  9. Craig, A. (n.d.). Entrapment neuropathies of the lower extremity. PM&R: The Journal of Injury, Function and Rehabilitation. 5(5 Suppl), S31-S40.
  10. Stoller DW, Rosenberg ZS, Cavalcanti C, et al. Entrapment neuropathies of the lower extremity. In: Stoller DW, ed. Magnetic Resonance Imaging in Orthopeaedics and Sports Medicine. Philadelphia, PA: Lippincott Williams & Wilkins; 2007:1051-1098.
  11. Aravindakannan T, Wilder-Smith EP. High-resolution ultrasonography in the assessment of merlagia parasthetica. Muscle Nerve. 2011;45:434-435.
  12. Nagpal, A., & Moody, A. (n.d.). Interventional Management for Pelvic Pain. Physical Medicine and Rehabilitation Clinics of North America., 28(3), 621-646.
  13. Soneji, N., & Peng, P. (n.d.). Ultrasound-guided pain interventions – a review of techniques for peripheral nerves. The Korean Journal of Pain., 26(2), 111-124.
  14. Gruber, H., Peer, S., Kovacs, P., Marth, R., & Bodner, G. (n.d.). The ultrasonographic appearance of the femoral nerve and cases of iatrogenic impairment. Journal of Ultrasound in Medicine., 22(2), 163-172.
  15. Martinoli, C., Miguel-Perez, M., Padua, L., Gandolfo, N., Zicca, A., & Tagliafico, A. (n.d.). Imaging of neuropathies about the hip. European Journal of Radiology., 82(1), 17-26.
  16. Kowalska, B., & Sudoł-Szopińska, I. (2012). Ultrasound assessment of selected peripheral nerves pathologies. Part II: Entrapment neuropathies of the lower limb. Journal of Ultrasonography., 12(51), 463-471.
  17. Petchprapa, C., Rosenberg, Z., Sconfienza, L., Cavalcanti, C., Vieira, R., & Zember, J. (n.d.). MR imaging of entrapment neuropathies of the lower extremity. Part 1. The pelvis and hip. Radiographics., 30(4), 983-1000.
  18. Boon AJ, Bailey PW, Smith J, Sorenson EJ, Harper CM, Hurdle MF. Utility of ultrasound-guided surface electrode placement in lateral femoral cutaneous nerve conduction studies. Muscle Nerve. 2011;44:525-530.
  19. Ducic I, Dellon L, Larson EE. Treatment concepts for idiopathic and iatrogenic femoral nerve mononeuropathy. Ann Plast Surg. 2005;55:397-401.
  20. Wadhwa, V., Scott, K., Rozen, S., Starr, A., & Chhabra, A. (n.d.). CT-guided Perineural Injections for Chronic Pelvic Pain. Radiographics., 36(5), 1408-1425.

Original version of the topic

Anita S.W. Craig, DO. Proximal lower extremity mononeuropathies. Original publication date: 10/22/2013.

Author Disclosure

Brionn K. Tonkin, MD
Nothing to Disclose

Deborah Hudleston, MD,
Nothing to Disclose

Alexander M Senk, MD
Nothing to Disclose