Femoral Nerve Tension Test
Definition/Description[edit | edit source]
The Femoral Nerve Tension Test, also known as the Femoral Nerve StretchTest (FNST) is a test used to screen for sensitivity to stretch soft tissue at the dorsal aspect of the leg, possibly related to nerve root impingements. It was first described by Wasserman in 1919. Literature suggests that this test is not used as commonly as the Straight Leg Raise (SLR) test because of less frequent upper lumbar radioculopathies as compared to lower lumbar radiculopathies. It is considered as an anterior corollary of SLR and assesses the mobility of upper lumbar nerve segments.
Purpose[edit | edit source]
The prone knee bending test is a neural tension test used to stress the femoral nerve and the mid lumbar (L2-L4) nerve roots.  The femoral nerve tension test is used to screen for sensitivity to stretch soft tissue at the dorsal aspect of the leg, possibly related to root impingements.
Clinically Relevant Anatomy[edit | edit source]
The Femoral Nerve comes from the Plexus Lumbosacralis (more specific the Plexus Lumbalis) and branches out into the N. Saphenus, the Rr. Musculares and the Rr. Cutanei Femoris Anteriores. This ramification happens usually about 2.5 cm under the inguinal ligament.
The femoral nerve lies within Scarpa’s triangle (or the ‘Trigonum Femorale Mediale’) which is bounded by the inguinal ligament (superiorly), the medial border of the Sartorius muscle and the lateral border of the Adductor Longus muscle (The muscles Pectineus and Iliacus and Psoas lie within this triangle as well). The femoral nerve lies (most laterally) next to the femoral artery and femoral vein (medially). 
Technique[edit | edit source]
The patient lies prone, and the therapist stands on the affected side and stabilizes the pelvis to prevent anterior rotation with one hand. With the other hand, the therapist then maximally flexes the knee to end range. If no positive signs are noted in this position, the therapist proceeds to extend the hip while maintaining knee flexion. The therapist can add a few alterations to the test position to identify the nerve involved. The Lateral Femoral Cutaneous Nerve bias test includes prone lying with passive hip extension adduction and knee flexion whereas the Sapheneous Nerve bias test includes prone-lying hip extension, abduction and external rotation with knee flexion, ankle dorsiflexion, and eversion.
Normal response: Knee flexion allowing the heel to touch the buttocks. A pull or a stretch is felt in the quadriceps.
If unilateral pain is produced in the lumbar region, buttocks, posterior thigh, between the ranges of 80-100 degrees of knee flexion in a combination of these regions, the test is considered positive. The dura is tensioned between 80 and 100 degrees and positive findings in this range could be indicative of a disk herniation affecting the L2, L3 or L4 nerve root. Positive findings secondary to a disc herniation can be differentiated from quadriceps problems based upon the range in which pain is reproduced. If pain is produced before 80 degrees of knee flexion, quadricep tightness and/or injury may be the cause. Also, if tightness exists, the pelvis rises on that side as hip flexes in response to passive knee flexion. As tight rectus femoris can also produce pain in the anterior thigh, thus it is important to perform the test on both sides and compare the symptoms.
Key Research[edit | edit source]
- In some cases, when a patient is suspected to have a lateral L4/5 disc protrusion, the femoral nerve tension test might induce ipsilateral sciatica. The L4 nerve root is moved downward and stretched when the femoral nerve tension test is performed. In Christodoulides’ research all patients (n=40) subjected to this test were verified using myleography (an examination that involves the injection of contrast material in the space around the spinal cord and nerve roots using a real-time form of x-ray called fluoroscopy) The criteria for selecting patients were only that they were suspected to have a lateral L4/5 disc protrusion. 
- The femoral nerve tension test can also be used to screen for high lumbar radiculopathy (a description for several symptoms, where the origination of the problem is near the root nerves in the spine, causing the nerves not to work properly ), but in some cases this may prove unreliable. For example, when an individual who has tight or injured muscles on the anterior side of his/her thigh undergoes this test, it might prove to be falsely positive, especially because the diagnosis is considered positive when it induces pain in the groin, anterior or posterior thigh, buttocks or lumbar region. 
- In research performed by Pradeep Suri and others, they experienced that the femoral nerve stretch test is one of the most reliable tests to screen for midlumbar (L2, L3 or L4 levels) nerve root impingement (results between 88 and 100%). The chances of this test being positive grow as the population ages and although pain is usually provoked only in the groin and anterior thigh, it may also be experienced in the calf, ankle or foot. In contrary to other research, the crossed femoral nerve stretch (performed similarly but with contralateral knee flexion) test didn’t provide additional gain in specificity. Individual physical examination tests such as the Femoral nerve stretch test may provide clinical information that substantially alters the likelihood that midlumbar impingement, low lumbar impingement, or level-specific impingement is present. Test combinations improve diagnostic accuracy for midlumbar impingement.
- A study evaluating hip flexor guarding or tightness using the Thomas test in conjunction with the prone knee banding test (PKB) to assess femoral nerve tension suggests a positive correlation between the Thomas Test and the Prone Knee Bend Test, suggesting a relationship between the femoral nerve's adverse neural tension and muscle length of the iliopsoas muscle. The findings indicate that increased femoral nerve tension may influence hip tightness in normal individuals and patients or adaptive shortening of the hip flexors may lead to adverse neural tension.
- Another research suggests falsely positive results secondary to tight or injured muscles of the anterior thigh, and to osseous or joint pathology in and about the hip. A case report suggests crossed FNST as an effective evaluation tool in diagnosing upper lumbar radiculopathy. The physical examinations of 2 patients suggested high lumbar radiculopathy, which was confirmed by both the FNST and crossed FNST. However, further study is necessary to identify its prevalence in the assessment of the high lumbar radiculopathy.
Evidence[edit | edit source]
The specificity and sensitivity of the test is unknown.
Resources[edit | edit source]
ADVERSE NEURAL TENSION Workbook.
References[edit | edit source]
- Orthopaedic Manual Physical Therapy From Art to Evidence, Chapter 19: The Theory and Practice of Neural Dynamics and Mobilisation. Christopher H Wise.
- Magee DJ. Orthopedic physical assessment. Elsevier Health Sciences; 2014 Mar 25.
- Shacklock M. Clinical neurodynamics: a new system of musculoskeletal treatment. Elsevier Health Sciences; 2005.
- Picture found on http://karate.butsu.net/anatomy/lumbosacral.html
- Schünke M, Schulte E, Schumacher U, Voll M, Wesker K. Prometheus anatomy. Houten: Bohn Stafleu van Loghum, 2005.
- Dutton, M. (2008). Orthopaedic: Examination, evaluation, and intervention (2nd ed.). New York: The McGraw-Hill Companies, Inc.
- ADVERSE NEURAL TENSION. Manual Therapy Institute Accessed on 4/9/2020 from https://mtitx.com/wp-content/uploads/2016/05/Adverse-neural-tension-workbook.pdf
- Orthopaedic Physical Therapy 3rd Edition, Robert Donatelli, Michael Wooden, Chapter 19: Evaluation and Treatment of Dysfunction in the Lumbar-Pelvic-Hip Complex
- John GibbonsHow to test the Femoral Nerve (Lumbar Plexus L2,3,4) or reverse Lasegue's. Available fromhttps://www.youtube.com/watch?v=cN0uou-nZH8
- Antonios N. Christodoulides. Ipsilateral Sciatica on femoral nerve stretch test is pathognomonic of an L4/5 protrusion. The Journal of Bone and Joint Surgery 1989; 71-B: 88-89. http://www.ncbi.nlm.nih.gov/pubmed/2915013 Level of evidence: C
- Scott F. Nadler, DO, Gerard A. Malanga, MD, Todd P. Stitik, MD, Rohit Keswani, MD, Patrick M. Foye, MD. The Crossed Femoral Nerve Stretch Test to Improve Diagnostic Sensitivity for the High Lumbar Radiculopathy: 2 Case Reports. Arch Phys Med Rehabil 2001; 82: 522-523. http://www.ncbi.nlm.nih.gov/pubmed/11295015 Level of evidence: B
- Pradeep Suri, MD, James Rainville, MD, Jeffrey N. Katz, MD, MS, Cristin Jouve, MD, Carol Hartigan, MD, Janet Limke, MD, Enrique Pena, MD, Ling Li, MPH, Bryan Swaim, MS, and David J. Hunter, MBBS, PhD. The Accuracy of the Physical Examination for the Diagnosis of Midlumbar and Low Lumbar Nerve Root Impingement. SPINE 2010, Lippincott Williams & Wilkins. (Published online ahead of print) http://www.ncbi.nlm.nih.gov/pubmed/20543768 Level of evidence: B
- Anloague PA, Chorny WS, Childs KE, Frankovich M, Graham C. The Relationship between Femoral Nerve Tension and Hip Flexor Muscle Length. J Nov Physiother. 2015;5(244):2.
- Nadler SF, Malanga GA, Stitik TP, Keswani R, Foye PM. The crossed femoral nerve stretch test to improve diagnostic sensitivity for the high lumbar radiculopathy: 2 case reports. Archives of physical medicine and rehabilitation. 2001 Apr 1;82(4):522-3.
- Magee DJ. Orthopedic physical assessment. Elsevier Health Sciences; 2014 Mar 25.