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Sciatica Unraveled Part 2: Non-Disc Causes & Diagnosis

Updated: Dec 5, 2023

In our initial segment, we delved into disc herniation's contribution to sciatica, emphasizing disc protrusions, extrusions, and sequestrations. We further discussed the preference for conservative therapy in addressing most disc herniations, provided there are no immediate concerns. Proceeding with our series on sciatica, this segment will encompass:

  • Non-discogenic triggers of sciatica, highlighting sciatic nerve tethering.

  • Direct impingement on the sciatic nerve.

  • Methods and criteria for diagnosing sciatica.

Article Index:

Non-Discogenic Sciatica

Examination & Diagnosis

Conclusion & References


Non-Discogenic Sciatic Nerve Pain

There are numerous types of non-discogenic syndromes that cause sciatic-like pain. Some of these are caused by restrictions in sciatic nerve motion (which can then lead to nerve entrapment) while other types involve direct sciatic nerve compression.

A non-discogenic cause of sciatica, where the sciatic nerve's freedom of movement is compromised, is referred to as "Deep Gluteal Syndrome" (DGS).

This condition involves the entrapment of nerves and blood vessels in the deep gluteal space, manifesting symptoms such as buttock and leg pain, numbness, and muscular weakness.

Contributors to DGS include:

  • Piriformis syndrome, where the piriformis muscle causes nerve and vascular compression due to its tightness or swelling.

  • Sciatic nerve compression by surrounding muscles, skeletal structures, or other tissues.

  • Vascular entrapment leading to diminished blood flow and tissue oxygenation in the deep gluteal space.

  • Traumatic events impacting the deep gluteal tissues, such as falls or vehicle collisions.

The characteristic pain of DGS often arises from fibrous collagenous bands that impede the nerve's natural gliding mechanism at different points along its path. Typically, the sciatic nerve adapts to the body's movements, stretching and sliding through adjacent tissue, thus distributing compressive forces encountered during daily activities.

However, in the case of DGS, these collagen bands restrict the nerve's movement, leading to neuropathy due to ischemia. These restrictive bands are usually situated lateral to (outside of) or medial to (inside of) the sciatic nerve's trajectory.


Fibrous Bands

Visual: The provided image offers a dual perspective of the sciatic nerve, showcasing a transverse view on the left and a longitudinal section on the right. Impressively, the sciatic nerve's maximum width rivals that of a human thumb!

Ongoing studies have pinpointed three primary variants of fibrous bands implicated in the sciatic nerve's entrapment:

  1. Bands composed solely of fibrous tissue.

  2. Bands with a mix of fibrous and vascular elements.

  3. Bands predominantly vascular in nature.

The role of these bands in sciatic nerve compression has been illuminated through endoscopic research. This technique, which utilizes an endoscope to inspect internal body spaces, has consistently revealed the presence of fibrous bands in patients with symptoms of sciatic nerve compression.

The locations where the sciatic nerve may become entrapped by these bands are diverse, including:

The sciatic nerve can become entrapped at several key anatomical sites due to fibrous bands. These sites include:

  • The area around the greater sciatic notch and ischial tuberosity.

  • Near the quadratus femoris muscle, specifically in the ischial tunnel region.

  • At the upper attachment points of the hamstring muscles, and further down at points along the hamstrings, often at sites of past injuries.

  • Within the region of the piriformis muscle and the adjacent obturator internus-gemelli complex.

Manifestations of Deep Gluteal Syndrome (DGS) can vary depending on the underlying issue and may or may not be associated with fibrous bands. Individuals with DGS might experience:

  • Severe buttock pain

  • Numbness or tingling sensations in the buttocks or legs

  • Weakness in the legs

  • Restricted movement in the hip joint

  • Pain that worsens with prolonged sitting or during certain activities

  • Pain or discomfort in the groin region


Direct Compression Of The Sciatic Nerve

Instances of the sciatic nerve being directly compressed can occur through conditions such as entrapment by the Piriformis muscle, Gemelli-Obturator Internus muscle, Quadratus Femoris muscle in Ischiofemoral impingement, or entrapments related to the Hamstring muscles. These scenarios may coincide with, or occur separately from, entrapments involving fibrous bands.

Piriformis Syndrome (PS)

Piriformis Syndrome, often presenting as back and buttock pain, is not always due to the fibrous bands linked with Deep Gluteal Syndrome (DGS). While biomechanical and genetic factors play a role, with women being more commonly affected (9), anatomical variations in the piriformis muscle itself are not definitive predictors of the syndrome.

Significantly, direct anatomical compression is only the cause in about 15% of Piriformis Syndrome cases (10). The predominant causes are environmental, like micro-trauma and post-surgical changes (11, 12). Tension in the piriformis fascia could also mimic sciatic nerve compression symptoms (17).

Care should be taken not to overdiagnose Piriformis Syndrome, especially when symptoms may suggest disc-related issues.


Gemelli-Obturator Internus Entrapment

The gemelli and obturator internus muscles are part of the lateral rotator group of the hip. This group consists of six small muscles responsible for laterally rotating the femur within the hip joint.

In this entrapment syndrome, the sciatic nerve is compressed between the piriformis muscle and the superior gemelli/obturator internus (13).

Both the obturator internus and the gemelli are enveloped by the obturator fascia, which is a continuation of the iliac fascia (17).

As we discuss fascial connections, it is essential to emphasize a crucial point: the anatomist's scalpel is what separates these six lateral rotator muscles. In reality, these muscles work together as a functional unit, and their fascial connections play a critical role in their integrated function.

During my time in the dissection lab, it became clear that the deep lateral rotator muscles of the hip are intricately linked through fascial tissue.

It's quite unrealistic to consider treating these muscles in isolation or to view them as functioning separately.

The interconnectedness of all lateral rotators, which I like to call the "magnificent six," means that they can affect each other's movement due to their fascial ties.

Frankly, anyone suggesting these muscles act independently might benefit from revisiting the dissection lab to observe these connections firsthand.

Photo Stecco, Carla; Stecco, Carla. Functional Atlas of the Human Fascial System E-Book (Page 313). Elsevier Health Sciences.


Quadratus Femoris - Ischiofemoral Entrapment

Ischiofemoral impingement involving the quadratus femoris muscle occurs when this muscle, stretching from the ischial tuberosity to the femur, exerts pressure on the adjacent sciatic nerve.

This syndrome is often due to a reduced gap between the femur and ischial tuberosity, making sitting and taking long strides while walking problematic.

While the precise cause of this condition is not well-defined, it's thought to relate to atypical hip dynamics, muscle imbalances, or structural variations in the femur or pelvic bones. Symptoms can include:

  • Hip, groin, or thigh pain

  • Numbness or a tingling sensation in the hip or thigh area

  • Muscle weakness in the hip or thigh

  • Limited hip movement

  • Pain exacerbated by sitting or during certain movements


Hamstring Related Entrapment's

Sciatic nerve function can be markedly affected by hamstring injuries. In the initial phase of such an injury, the resulting swelling can irritate the sciatic nerve.

With ongoing hamstring issues, persistent inflammation could lead to scarring (fibrosis) among the muscles, tendons, and fascial layers, potentially entrapping the sciatic nerve during hip movements.

Factors contributing to hamstring-associated sciatic nerve entrapment include:

  • Continuous or repetitive activities that strain the hamstring muscles like running or cycling, leading to muscle inflammation and tightness.

  • Direct impact from injuries such as falls or accidents that harm the hamstring muscles.

  • Natural variations in the anatomy that may predispose to a tighter space for the sciatic nerve, enhancing the likelihood of nerve compression.

The symptoms indicative of this form of sciatic nerve entrapment encompass:

  • Intense pain in the buttocks

  • Numbness or tingling sensations in the buttocks or legs

  • Leg weakness

  • Pain that escalates during sitting or certain movements

  • Decreased hip joint flexibility

  • Groin discomfort

It's important to recognize that conditions like sciatic nerve tethering or its direct compression can still be related to issues with the intervertebral disc. Furthermore, it's worth mentioning that anatomical compression, seen in disorders like Piriformis Syndrome, represents a relatively small proportion — approximately 15% — of such cases (10).


Physical Examination

Patients with symptoms resembling sciatica need a complete evaluation, including medical history, physical observation, and orthopedic and neurological tests, to determine if their condition is mechanical or indicative of deeper pathology.

The orthopedic assessment is key for diagnosing lower back issues. It starts with a visual check and motion tests of the lumbar spine, followed by palpation for sore spots. Tests like the Straight Leg Raise and others assess nerve function and identify conditions like disc herniation. Additional tests evaluate hip and leg mechanics, while the Homans Test screens for deep vein thrombosis. This rigorous evaluation is critical for accurately diagnosing and treating lumbar spine disorders.

Orthopedic Assessment Video

Low Back Examination

To observe a demonstration of the standard orthopedic tests conducted during a clinical examination of the low back, click on the video located to the right. The video showcases various tests that are commonly used to diagnose musculoskeletal conditions that affect the lower back.


Neurological/Vascular Testing

A comprehensive neurological exam is vital for diagnosing musculoskeletal issues. It should assess sensation changes via dermatomal patterns—though these may vary between individuals and lack unanimous chart agreement—and deep tendon reflexes, which signal peripheral or central nervous system integrity, graded on a 0 to 4 scale at key reflex points.

Motor function is gauged through myotomes, with muscle strength rated from 0 (no contraction) to 5 (full motion against resistance) at specific muscle sites. Plain radiographs are advised for older patients, or those with significant risk factors or symptoms. The Babinski sign, if present, points to an upper motor neuron issue. This in-depth neurological assessment aids in pinpointing and managing musculoskeletal disorders.

Lower Limb Neuro Examination video

The Lower Limb Neurological Examination is an essential component of the overall neurological examination process, and is performed to evaluate the sensory and motor neurons that supply the lower limbs. This examination aids in identifying any dysfunction in the nervous system, and serves as a valuable screening and investigative tool.

Peripheral Vascular Examination - Video

Conducting a peripheral vascular examination is a vital means of identifying any signs of vascular-related pathology, and can help prevent cardiovascular and cerebrovascular complications. This examination is a valuable tool for ruling out any possible issues. The video presented here demonstrates some of the most commonly used procedures in daily clinical practice.


Orthopaedic Physical Assessment – David J. Magee

Dutton's Orthopaedic: Examination, Evaluation and Intervention, Fifth Edition



Imaging plays a crucial role in the diagnosis of sciatica and identifying the underlying cause of nerve root compression. Several imaging modalities are utilized to evaluate patients with sciatica, including X-ray, magnetic resonance imaging (MRI), ultrasound, and other imaging procedures.


X-ray imaging is often used to rule out other possible conditions, such as a fracture or tumor. However, X-rays have limited utility in diagnosing sciatica because they cannot visualize the soft tissues or nerves.


MRI is considered the gold standard for evaluating patients with sciatica, providing detailed images of the spinal cord, nerve roots, and surrounding soft tissues. It is highly sensitive and can identify herniated discs, spinal stenosis, and other abnormalities that may be compressing the nerve roots.


Ultrasound imaging can be used to visualize the sciatic nerve and its surrounding structures, providing real-time images of nerve compression and potential entrapment sites. It is often used for diagnosing piriformis syndrome and other causes of sciatica.

Other imaging procedures that may be used to diagnose sciatica include computed tomography (CT) scans and myelography. CT scans provide detailed images of the bones and soft tissues, while myelography uses contrast dye to highlight the spinal cord and nerve roots, making them more visible on X-ray or CT images.


Conclusion Part - 2

In conclusion, there are various non-discogenic syndromes that can cause sciatic-type pain. Some of these syndromes involve restricting sciatic nerve motion or direct compression of the sciatic nerve, while others involve fibrous bands that can decrease sciatic nerve mobility and cause sciatic neuropathy. Direct compression only accounts for about 15% of cases, while other syndromes are more prevalent.

It is essential to perform a complete physical examination that includes a comprehensive history to accurately diagnose sciatica. When a patient presents with back and leg pain, and the leg pain is worse than the back pain, it is crucial to consider disc-related issues until proven otherwise. If a patient's leg pain becomes low back pain, disc-related issues are likely the cause. The diagnostic process is ongoing, and a working diagnosis may change over time. Therefore, examining, re-examining, and re-examining again is crucial.

In the next part of this series, "Sciatica - Treatment - Logic & Recommendations," we will discuss conservative treatment options for sciatica, including spinal manipulation/mobilization and myofascial release procedures.



Dr. Abelson's approach in musculoskeletal health care reflects a deep commitment to evidence-based practices and continuous learning. In his work at Kinetic Health in Calgary, Alberta, he focuses on integrating the latest research with a compassionate understanding of each patient's unique needs. As the developer of the Motion Specific Release (MSR) Treatment Systems, he views his role as both a practitioner and an educator, dedicated to sharing knowledge and techniques that can benefit the wider healthcare community. His ongoing efforts in teaching and practice aim to contribute positively to the field of musculoskeletal health, with a constant emphasis on patient-centered care and the collective advancement of treatment methods.


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References Part - 2

  1. Lewis AM, Layzer R, Engstrom JW, Barbaro NM, Chin CT. Magnetic resonance neurography in extraspinal sciatica. Arch Neurol. 2006;63(10):1469–72.

  2. Martin HD, Kivlan BR, Palmer IJ, Martin RL. Diagnostic accuracy of clinical tests for sciatic nerve entrapment in the gluteal region. Knee Surg Sports Traumatol Arthrosc. 2014;22(4):882–8.

  3. Hernando MF, Cerezal L, Pérez-Carro L, Abascal F, Canga A. Deep gluteal syndrome: anatomy, imaging, and management of sciatic nerve entrapments in the subgluteal space. Skeletal Radiol. 2015;44(7):919–34.

  4. Martin HD, Shears SA, Johnson JC, Smathers AM, Palmer IJ. The endoscopic treatment of sciatic nerve entrapment/deep gluteal syndrome. Arthroscopy. 2011;27(2):172–81. [PubMed]

  5. 12. Spinner RJ, Tiel RL. Sciatic nerve compression and piriformis syndrome. In: Midha R, Zager EL, editors. Surgery of Peripheral Nerves : A Case-Based Approach. New York: Thieme; 2008. pp. 186–191.

  6. Adams JA. The pyriformis syndrome -- report of four cases and review of the literature. S Afr J Surg. 1980;18:13–18.

  7. Lohrer H, Nauck T, Konerding MA. Nerve entrapment after hamstring injury. Clin J Sport Med. 2012 Sep;22(5):443-5.

  8. Luis Perez Carro, Moises Fernandez Hernando, Luis Cerezal, Ivan Saenz Navarro, Ana Alfonso Fernandez, and Alexander Ortiz Castillo1 Deep gluteal space problems: piriformis syndrome, ischiofemoral impingement and sciatic nerve release Muscles Ligaments Tendons J. 2016 Jul-Sep; 6(3): 384–396.

  9. Klein MJ. Piriformis syndrome. eMedicine Specialities: Physical Medicine and Rehabilitation: Lower limb Musculoskeletal conditions 2010 fckLR

  10. Lori A, Boyajian-O’ Neill, et al. Diagnosis and management of piriformis syndrome:an osteopathic approach. J Am Osteopath Assoc Nov 2008;108(11):657-664

  11. Tonley JC, Yun SM, et al. Treatment of an individual with piriformis syndrome focusing on hip muscle strengthening and movement reeducation: a case report. J Orthop Sports Phys Ther 2010;40(2):103-111.

  12. Lori A, Boyajian-O’ Neill, et al. Diagnosis and management of piriformis syndrome:an osteopathic approach. J Am Osteopath Assoc Nov 2008;108(11):657-664.

  13. Filler AG, Gilmer-Hill H. Piriformis syndrome, obturator internus syndrome, pudendal nerve entrapment, and other pelvic entrapments. In: Winn HR, editor. Youmans neurological surgery. 6th ed. Philadelphia: Saunders; 2009. pp. 2447–55.

  14. Taneja AK, Bredella MA, Torriani M. Ischiofemoral impingement. Magn Reson Imaging Clin N Am. 2013;21(1):65–73.

  15. Torriani M, Souto SC, Thomas BJ, Ouellette H, Bredella MA. Ischiofemoral impingement syndrome: an entity with hip pain and abnormalities of the quadratus femoris muscle. AJR Am J Roentgenol. 2009;193(1):186–90.

  16. Bucknor MD, Steinbach LS, Saloner D, Chin CT. Magnetic resonance neurography evaluation of chronic extraspinal sciatica after remote proximal hamstring injury: a preliminary retrospective analy-sis. J Neurosurg. 2014;121(2):408–14. [PubMed]

  17. Stecco, Carla; Stecco, Carla. Functional Atlas of the Human Fascial System. Elsevier Health Sciences.

  18. Dr. Shawn Thistle - RRS Education - Chiropractic Care for Disc Patients April 28th 2019


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