Musculoskeletal mimics of lumbosacral radiculopathy

Abstract

Electrodiagnostic evaluations are commonly requested for patients with suspected radiculopathy. Understanding lower extremity musculoskeletal conditions is essential for electrodiagnostic medicine specialists, as musculoskeletal disorders often mimic or coexist with radiculopathy. This review delineates radicular pain from other types originating from the lumbosacral spine and describes musculoskeletal conditions frequently mimicking radiculopathy, such as those that cause radiating pain and sensorimotor dysfunction. In clinical evaluation, a history of pain radiating along a specific dermatomal territory with associated sensory disturbance suggests radiculopathy. Physical examination findings consistent with radiculopathy include myotomal weakness, depressed or absent muscle stretch reflexes, focal atrophy along a discrete nerve root territory, and potentially positive dural tension maneuvers like the straight leg raise. However, electrodiagnostic medicine specialists must be knowledgeable of musculoskeletal mimics, which may manifest as incomplete radiation within or beyond a dermatomal territory, non‐radiating pain, tenderness, and give‐way weakness, in the context of a normal neurological examination. A systematic approach to musculoskeletal examination is vital, and this review focuses on high‐yield physical examination maneuvers and diagnostic investigations to differentiate between musculoskeletal conditions and radiculopathy. This approach ensures accurate diagnoses, promotes resource stewardship, enhances patient satisfaction, and optimizes care delivery. Musculoskeletal conditions resembling L1 to S4 radiculopathy are reviewed, emphasizing their distinctive features in history, physical examination, and diagnostic investigation. Among the more than 30 musculoskeletal disorders reviewed are hip and knee osteoarthritis, lumbar facet syndrome, myofascial pain syndrome, greater trochanteric pain syndrome, and plantar fasciitis.

Abbreviations

+LR

positive likelihood ratio

−LR

negative likelihood ratio

AVN

avascular necrosis

DXA

dual‐energy x‐ray absorptiometry

EDX

electrodiagnostic testing

FABER

flexion, abduction, and external rotation

FADIR

flexed, adducted and internally rotated

FAI

femoroacetabular impingement

GTPS

greater trochanteric pain syndrome

IT

Iliotibial

MR

magnetic resonance

OA

osteoarthritis

OR

odds ratio

PF

plantar fasciitis

PPV

positive predictive value

ROM

range of motion

SIJ

sacroiliac joint

US

ultrasound

1. INTRODUCTION

Low back pain is among the top reasons why patients seek medical care, is responsible for more disability than any other musculoskeletal condition, and has significant direct and indirect economic and health care costs. ¹ , ² , ³ Low back pain is often associated with concurrent but distinct pain conditions including referred pain, radicular pain, and radiculopathy, all of which are common presenting features in patients referred for electrodiagnostic assessment. ⁴ , ⁵ However, not all pain that also affects or radiates to the buttock, thigh, or leg is caused by compression of lumbosacral spinal nerve roots. ⁶

The differential diagnosis for back pain radiating or extending into the lower limb is broad, as multiple structures and conditions can produce back and lower extremity pain, including lumbosacral radiculopathy, non‐radiculopathy disorders of the peripheral nervous system, disorders of the central nervous system, and musculoskeletal disorders. ⁵ , ⁷ Musculoskeletal disorders, the focus of this review, can mimic and/or occur concurrently with lumbosacral radiculopathy. For example, estimates of the prevalence of lumbosacral radiculopathy range from 3% to 5% of the adult population, far lower than the point prevalence of low back pain (10%–30%) or greater trochanteric pain syndrome (GTPS) (6.6%–15%), which are just two of many mimics. ⁸ , ⁹ , ¹⁰ , ¹¹ , ¹² This underscores the importance of being able to correctly identify radiculopathy with or without other concomitant musculoskeletal diagnoses.

Numerous musculoskeletal disorders outside of the lumbosacral spine can mimic the pain that often accompanies lumbosacral radiculopathy. Moreover, numerous musculoskeletal disorders can be present concurrently with lumbosacral radiculopathy and/or present in persons referred for lumbosacral radiculopathy with normal electrodiagnostic testing (EDX) or other, non‐radiculopathy peripheral nerve disorders. ⁵ For instance, Cannon et al. found that among 170 persons referred for EDX for suspected lumbosacral radiculopathy, nearly 1 in 3 had at least one of myofascial pain syndrome, iliotibial (IT) band or greater trochanteric pain syndrome, or plantar fasciitis (PF). ⁵ As such, providers of electrodiagnostic evaluation of lumbosacral radiculopathy ought to have a solid working knowledge of musculoskeletal disorders, particularly those whose symptoms may imitate those of radiculopathy.

The objective of this review is to provide an evidence‐informed synthesis of common musculoskeletal disorders and their presenting features and contrast them with lumbosacral radiculopathy to help electrodiagnostic medicine specialists and other health care providers arrive at appropriate diagnoses.

2. DEFINITIONS

Bogduk previously synthesized the definitions of key components of the lumbosacral pain syndromes. ⁴ These pain syndromes—nociceptive back pain, somatic referred pain, radicular pain, and radiculopathy—are summarized here. In nociceptive back pain, pain arises from noxious stimulation and/or pain generators within the lumbosacral spine including lumbosacral intervertebral discs, interspinous and other ligaments, facet joints, and sacroiliac joints. ¹³ In somatic referred pain, noxious stimulation and/or pain generators in the lumbosacral spine produce pain that is perceived in regions away from the site of the pain generator but typically in regions with the same innervation as the pain generator. In radicular pain, noxious stimulation arising from the spinal nerve roots, particularly the dorsal root or its ganglion, produces pain that radiates the length of the lower extremity. In radiculopathy, neurological impairment of motor and/or sensory function arises from injury to one or more spinal nerve roots, which may or may not also have radicular pain. ⁴ Other definitions of radiculopathy center on the compression of spinal nerve root(s) resulting in pain, weakness, or numbness in a myotomal or dermatomal distribution (Figure 1). ¹⁴ Critically, many of these types of pain can present in distributions that overlap with dermatomal areas, but they may also generate referred pain that does not conform to one or more dermatomal distributions.

FIGURE 1.

Lower extremity dermatomes.

Many of the conditions described in this review may present with pain, weakness, and/or sensory changes, like radiculopathy. The focus of this review is on painful musculoskeletal mimics of lumbosacral radiculopathy, rather than the differential diagnosis of neurological conditions which may mimic radiculopathy‐related weakness and/or sensory changes. For the clinician assessing a patient with suspected radiculopathy, it is important to note that some neuropathic pain conditions and somatic referred pain can mimic the pain that often accompanies radiculopathy. Moreover, some musculoskeletal conditions can cause weakness and/or sensory loss. For instance, knee osteoarthritis (OA) is frequently associated with weakness of quadriceps femoris and patient reports of knee instability or weakness. ¹⁵ , ¹⁶

3. RELEVANT FEATURES OF RADICULOPATHY

Radiculopathy is a syndrome of neurological impairment of sensory and/or motor function of a spinal nerve root that arises from nerve root injury or compression. Patients' symptoms and signs vary depending on which nerve root is affected, as outlined in Table 1 and Figure 1. Although the precise frequency of lumbosacral radiculopathies is unknown, the vast majority involve the L5 and/or S1 nerve roots, as the L4/L5 and L5/S1 intervertebral discs are the most likely to herniate. ¹⁸ Depending on the direction of herniation, either the L5 and/or S1 nerve root can be affected. ¹² , ¹⁴ , ¹⁸ Like radiculopathy from disc herniation, radiculopathy due to other etiologies, including degenerative spondyloarthropathy, typically resolve spontaneously in weeks to months but may persist in some patients. ¹⁴ , ¹⁹ , ²⁰

TABLE 1.

Common features of radiculopathies by level.

Root Level (frequency)	Location of pain	Distribution of sensory loss or paraesthesiae	Pattern of motor weakness a	Other clinical exam findings
L1	Inguinal region	Inguinal region	Hip flexion
L2	Anterior groin Anterior proximal thigh	Anterior proximal thigh	Hip flexion
L3 (≤5% 17 )	Anterior mid‐thigh Medial knee	Medial thigh Medial knee	Knee extension Hip adduction	May have reduced or absent patellar reflex
L4 (≤5% 17 )	Medial leg	Medial leg	Knee extension Hip adduction Dorsiflexion	May have reduced or absent patellar reflex
L5 (95% 18 )	Anterolateral leg Dorsum of foot	Anterolateral leg Dorsum of foot	Dorsiflexion Toe extension Ankle inversion Ankle eversion Knee flexion Hip abduction	May have reduced or absent medial hamstring reflex; may have reduced or absent ankle evertor reflex
S1 (95% 18 )	Posterior thigh Posterior leg Plantar surface of foot	Plantar surface of foot	Plantarflexion Toe flexion Knee flexion Hip extension	May have reduced or absent Achilles reflex
S2‐4 b	Medial buttocks Posterior thigh	Medial buttocks Posterior thigh Perineum	Knee flexion Hip extension	May have reduced anal sphincter tone; may have reduced or absent anal wink and/or bulbocavernosus reflexes

^a Due to muscles receiving innervation from more than one myotome, monoradiculopathies may not produce weakness.

^b Often involved together because of close anatomic relationships. ¹²

Radiculopathy often, but not always, includes radiating pain and/or sensory loss along dermatomal territories, and can be termed “sciatica” by patients and healthcare providers. ¹² The character of the pain may be neuropathic—burning, electric—or may be described as dull or aching. ¹² Patients may or may not have concurrent low back pain. ⁸ Factors on history that correlate highly with nerve root impingement on imaging and/or radiculopathy on EDX include pain that radiates within a specific dermatome (odds ratio [OR] 4.1), pain with coughing or sneezing (OR 3.2), subjective muscle weakness (OR 2.2), and subjective sensory loss (OR 2.1). ²¹

Physical examination tests have poor sensitivity and/or specificity for identifying radiculopathy when used in isolation, whether radiculopathy is due to disc herniation or other causes. ¹⁴ , ²² Nevertheless, recommended physical examination maneuvers for the diagnosis of lumbosacral radiculopathy include: manual muscle testing (positive predictive value [PPV] of ankle dorsiflexion weakness 69% and lateral four toe extension weakness 76% for L4/5 radiculopathy), sensory testing (PPV 76% and 50% for sensory abnormalities in the L5 and S1 dermatomes, respectively), supine straight leg raise (sensitivity 0.67, superior to the seated straight leg raise, sensitivity 0.41), supine Lasegue's sign (sensitivity 0.77–0.83), and supine crossed Lasegue's sign (specificity 0.74–0.89). ¹⁴ , ²³ , ²⁴ , ²⁵

Other physical examination maneuvers which may aid in diagnosing lumbosacral radiculopathy include reflexes at the patellar and Achilles tendons. Ipsilateral absent or reduced reflexes at the patellar tendon (sensitivity 0.18–0.67; specificity 0.66–0.90) and Achilles tendon (sensitivity 0.14–0.67; specificity 0.60–0.93) suggest patients may have L4 or L5/S1 radiculopathies, respectively. ²⁶

Imaging modalities, particularly MRI, are frequently used to investigate low back pain and/or suspected radiculopathy. ²⁷ , ²⁸ However, abnormalities on MRI are highly prevalent, even among persons who are asymptomatic. ²⁹ , ³⁰ Consequently, resource stewardship organizations such as Choosing Wisely (USA) and Choosing Wisely Canada, as well as numerous specialty societies recommend judicious selection of patients who require imaging as well as appropriate use of imaging modalities. ³¹ In one systematic review, the sensitivity of MRI for detecting lumbosacral radiculopathy was 0.25 and the specificity was 0.92. ³² Thus MRI may have value in confirming the presence of radiculopathy in patients with symptoms that have not resolved and who are considering surgical intervention.

4. MUSCULOSKELETAL MIMICS OF RADICULOPATHY BY LEVEL (L1–S4)

Landmarks for palpation tenderness relevant to the assessment of these conditions are illustrated in Figure 2. Musculoskeletal mimics of L1 radiculopathies tend to cause pain in the inguinal region; epidemiologically, L1 radiculopathies are rare, and clinicians should strongly consider the possibility of an alternative diagnosis. Similarly, L2 radiculopathies are rare; for patients with pain in the groin and proximal thigh referred for suspected L2 radiculopathy, the examining clinician should strongly consider other diagnoses. Radiculopathy affecting the L3 nerve root, which typically causes pain in the medial knee, is uncommon, whereas musculoskeletal conditions which reproduce pain in this region are common. Radiculopathies affecting the L4 nerve root, which causes pain in the medial leg, are also uncommon compared to L5 and S1 radiculopathies, but more common than L1–L3 radiculopathies. ¹⁷ Although L5 and S1 radiculopathies, which typically cause pain in the anterolateral leg and posterior thigh, respectively, comprise the bulk of lumbosacral radiculopathies, conditions which mimic radicular pain in these distributions are also common. ⁵ , ¹⁸ Common musculoskeletal mimics of radiculopathy are summarized in Table 2.

FIGURE 2.

Selected anatomical landmarks for palpation tenderness on physical examination. Palpation of the above landmarks can be useful for identifying potential generators of patients' pain. The presence of pain on palpation at these landmarks as part of a comprehensive history and physical examination may suggest the patient has a painful musculoskeletal condition; this does not exclude concurrent radiculopathy.

TABLE 2.

Common mimics by location of pain.

Spinal root level	Mimicking condition	Key features	Key physical exam findings	Investigations and/or diagnostic tests
L1	Hip OA (also mimics L3 and L4)	Groin pain worse with activity	Reduced hip ROM; Pain with ROM	Plain x‐ray; hip intraarticular injection
	Femoral head avascular necrosis	Groin pain worse with activity	Reduced hip ROM; pain with ROM	MRI
	Labral tears and/or femoroacetabular impingement	Groin pain worse with activity	FABER; FADIR; scour test	Plain x‐ray; MR arthrogram; hip intraarticular injection
	Athletic Pubalgia (also mimics L2)	Groin or lower abdominal pain	Pain at the pubic tubercles and rectus abdominis and/or adductor muscle origins	MRI
L2	Occult femoral neck fracture or femoral neck stress fracture	Groin pain worse with activity	Pain to palpation; hop test; fulcrum test	MRI
	Iliopsoas bursitis or tendinopathy	Anterior hip region pain	Pain to palpation; Thomas test	US; MRI; Iliopsoas injection
L3	Greater trochanteric pain syndrome (also mimics L4 and L5)	Lateral hip pain worse with activity and ipsilateral side lying	Pain to palpation	US; GT bursal injection
	Iliotibial band syndrome (also mimics L4 and L5)	Lateral knee and/or leg pain worse with activity	Pain to palpation of the lateral knee; palpable snap of the ITB over the lateral femoral condyle; Noble compression test	Clinical; dynamic US if in doubt
	External snapping hip syndrome (coxa saltans)	Lateral hip pain with audible or palpable snap	Palpable or audible snap over greater trochanter	Clinical; dynamic US if in doubt
L4	Quadriceps muscle contusion or strain	Anterior thigh pain	Pain with passive knee flexion and/or hip extension, or with resisted knee extension	US; MRI
	Knee OA (also mimics L3)	Knee pain worse with weightbearing	Pain to palpation of medial/lateral joint line; varus/valgus deformity	Plain x‐ray
L5	Piriformis syndrome	Buttock and/or thigh and leg pain	Pain with active or passive piriformis tension	MR
	Exertional compartment syndrome	Leg pain and/or numbness or paraesthesiae with activity	Examination is normal	Intracompartment pressure monitoring during exercise
	Tibial and/or fibular stress syndrome	Leg pain with activity	Focal tenderness ≥5 cm along the tibia or fibula	Plain x‐ray to rule out stress fracture
S1	Hamstring strain or tendinopathy	Buttock and posterior thigh pain	Pain with resisted knee flexion and/or passive knee extension	US; MRI
	Ischiofemoral impingement	Posteromedial buttock pain worse with hip extension	Long stride walking test	MRI
	Ischiogluteal bursitis	Buttock and/or posterior thigh pain worse with sitting	Pain to palpation of the IT	US; MRI IT bursal injection
	Sacroiliac joint dysfunction	Low back and/or buttock pain, especially with transitions	≥3 positive provocative tests	MRI; SIJ injection
	Plantar fasciitis	Plantar surface heel pain	Windlass test; pain on palpation	Clinical; plain x‐ray or US if in doubt
S2‐4	Gemellus/obturator internus syndrome	Posterior buttock pain	Pain with passive hip internal rotation	MRI
	Coccydynia	Pain at the coccyx (“tailbone”) worse with sitting	Pain with palpation of coccyx	Plain x‐ray sitting and standing
Any of the above	Myofascial pain syndrome	Varies	Pain on palpation of taut muscle bands with reproduction of radiating pain (trigger points)
	Lumbar facet syndrome and interspinous ligament pain	Axial low back and/or buttock pain, often worse with activity	Pain on palpation of facet joints or paraspinal muscles; pain with axial lumbar spine range of motion

Abbreviations: FABER, flexion, abduction, external rotation; FADIR, flexion, adduction, internal rotation; GT, greater trochanter; IT, ischial tuberosity; ITB, iliotibial band; MR, magnetic resonance; MRI, magnetic resonance imaging; OA, osteoarthritis; ROM, range of motion; SIJ, sacroiliac joint; US, ultrasound.

Whereas some of the mimics discussed in this section produce pain that mimics a single‐level radiculopathy, some diagnoses, such as hip osteoarthritis, piriformis syndrome, myofascial pain syndrome, and lumbar facet syndrome, can mimic radiculopathies at multiple levels. Many but not all of the musculoskeletal mimics outlined in this review can be identified with palpation of key structures (Figure 2). In general, musculoskeletal disorders are more likely to have associated focal palpation tenderness—or, for myofascial pain, diffuse tenderness—which can be a useful physical examination maneuver for identifying mimics existing concurrently with radiculopathy and/or causing the patient's symptoms in the absence of radiculopathy.

4.1. L1 radiculopathy mimics

Many of the mimics of L1 radiculopathy are pathologies of the hip joint. In general, when trying to distinguish radiculopathy and hip joint pathology, a diagnostic hip joint injection can be helpful to clarify whether the etiology of the pain is from the hip joint with >90% accuracy. ³³ , ³⁴

4.1.1. Hip osteoarthritis

Osteoarthritis of the hip joint causes symptoms in 4.2% of the population. It is more commonly seen in adults aged 60 years and over, for whom the prevalence of symptomatic hip OA rises to 6.3%–7.4%. ³⁵ Although hip OA classically presents as groin pain that is worse with activity, referred pain from the hip joint to surrounding areas can mimic the radiating pain of a lumbosacral radiculopathy. ³⁶ In one case series of 43 patients with hip OA, 44% were initially treated for lumbosacral spine pathology without the hip osteoarthritis having been recognized. ³⁷ A family history of OA (sensitivity 0.34; specificity 0.84; positive likelihood ratio [+LR] 2.1), a personal history of knee OA (sensitivity 0.33; specificity 0.84; +LR 2.1), and pain when climbing stairs or walking down slopes (sensitivity 0.68; specificity 0.68; +LR 2.1) are predictive of hip OA. ³⁸ Conversely, age less than 60 years (sensitivity 0.96; specificity 0.25; +LR 0.11) and the absence of pain during walking (+LR 0.25–0.58) suggest that hip osteoarthritis is less likely. ³⁸

The two physical exam maneuvers that are the most specific for diagnosing hip osteoarthritis are posterior pain during squatting (sensitivity 0.24; specificity 0.96; +LR 6.1) and groin pain on passive hip abduction or adduction (sensitivity 0.33; specificity 0.94; +LR 5.7); normal hip adduction range of motion (ROM) was the most useful for ruling out hip osteoarthritis (negative likelihood ratio [−LR] 0.25). ³⁸ Plain radiographs of the hip joint identify osteoarthritis, but approximately three‐quarters of radiographic hip osteoarthritis is asymptomatic. ³⁵ The presence of hip OA on plain radiographs also does not preclude the concomitant diagnosis of a radiculopathy. However, unlike lumbosacral radiculopathy, pain from hip osteoarthritis could respond to intraarticular diagnostic injections (sensitivity 0.97; specificity 0.91), which, together with the aforementioned physical exam maneuvers, can help distinguish it from an L1 radiculopathy. ³⁹

4.1.2. Avascular necrosis of the femoral head

Femoral head avascular necrosis (AVN) occurs when disruption of the blood supply to the femoral head leads to bone death over months to years. ⁴⁰ AVN typically presents with groin pain or vague pain around the hip region, which can be mistaken for other disease conditions such as radiculopathy. ⁴⁰ , ⁴¹ In one retrospective case series, 38% of patients who were not given their initial correct diagnosis of AVN were misdiagnosed as having lumbar disc herniation. ⁴² This diagnosis should be suspected in young people with groin pain, especially if they have risk factors that are etiological factors for AVN. If left untreated, AVN will lead to collapse of the femoral head and worse outcomes compared to patients identified in the early stages of the disease, underscoring the importance of early recognition. ⁴³

AVN generally affects a younger population, with age at first treatment averaging between 33 and 38 years old. ⁴¹ The etiology of AVN can be idiopathic or attributable to a wide range of causes including steroid use, alcohol use, sickle cell anemia, radiation, trauma, and vasculitis. ⁴⁰ Physical exam maneuvers to aid in diagnosis include assessing for decreased hip ROM and tests for intraarticular hip joint pathology (see next section).

Plain radiographs have a low sensitivity of detecting the disease, particularly in the early stages. ⁴⁴ MRI has a sensitivity >0.90 when compared with surgical pathology. ⁴⁵ , ⁴⁶ Although hip intraarticular injections can be used to identify pathology within the hip joint, such as AVN, and to distinguish it from radiculopathy, hip joint injections should be used with caution in this condition as they can contribute to progression of AVN. ⁴⁷

4.1.3. Labral tears

Two hip joint pathologies that mimic lumbosacral radiculopathy are labral tear and femoroacetabular impingement (see next section). Like AVN, these conditions are more common in younger adults.

The labrum of the hip joint is the fibrocartilaginous tissue that surrounds the acetabulum which plays a role in shock absorption, joint stability, and pressure distribution. ⁴⁸ , ⁴⁹ Labral tears are associated with athletic activities and affect up to 55% of athletes who present with hip pain along with mechanical symptoms such as clicking, locking, and instability. ⁴⁹ Labral tears are more common in women, particularly between 15 and 41 years of age. ⁴⁸ Labral tears typically present with anterior groin pain, with nearly all patients who have arthroscopically diagnosed labral tears noting this symptom. ⁴⁸ , ⁵⁰ , ⁵¹ However, pain attributable to labral tears can be felt in the lateral hip, or radiate to the buttocks or the knees, mimicking lumbosacral radiculopathy. ⁴⁸ , ⁵⁰ Acetabular labral tears can be caused by trauma, joint hypermobility, age‐related degeneration, hip dysplasia such as shallow acetabulum and femoral/acetabular anteversion, and femoroacetabular impingement. ⁴⁸

There are no specific physical exam maneuvers that distinguish an acetabular labral tear from other forms of intraarticular hip pathology such as osteoarthritis or AVN, but the Flexion, ABduction, and External Rotation (the FABER test or maneuver) is commonly used to diagnose intraarticular hip pathology. ⁵⁰ The FABER test is positive when there is anterior hip/groin pain when the hip is placed in the Flexed, Abducted and Externally Rotated hip position. ⁴⁹ In one small case series, the sensitivity of the FABER test was 0.88 for intraarticular hip pathology identified on hip arthroscopy. ⁵² Another labral test is the hip scour test; it has a sensitivity 0.62 and a specificity 0.75 for detecting hip intraarticular pathology. ⁵⁰ , ⁵³ The scour test is positive if it elicits groin pain and is performed with the hip in flexion, while an axial loading force is applied as the hip moves into abduction with hip external rotation and then adduction with hip internal rotation. ⁵⁴ Because the scour test also loads the lumbosacral spine, it may elicit low back pain; therefore, it is important to note the location of the patient's pain when performing this test. ⁵⁰ , ⁵³

Because of the low clinical exam reliability, diagnosis of a labral tear requires imaging. ⁵³ Plain radiographs should be done as an initial investigation (including Dunn views, see below); if joint space narrowing is present, further imaging is not recommended but diagnostic injection may be worthwhile. ⁵⁵ In persons <50 years old without joint space narrowing, magnetic resonance (MR) imaging can be considered. ⁵⁵ MR arthrogram is the best available imaging modality, with a sensitivity of 0.87 and specificity of 0.64, whereas MRI has a sensitivity of 0.66 and specificity of 0.79. ⁵⁶

4.1.4. Femoroacetabular impingement

Femoroacetabular impingement (FAI) is a condition that often co‐occurs with labral tears. FAI is not necessarily pathological, and exists as a normal anatomical variant in 20% of people. ⁴⁸ , ⁴⁹ However, 23% of people with FAI will experience hip pain as a result of additional bone on the femur surface (cam lesion), the acetabular surface (pincer lesion) or both impinging the articular cartilage of the hip joint. ⁴⁹ Like labral tears, FAI can mimic radiculopathy. FAI is associated with labral tears in 59.6% of symptomatic hip joints, and >40% in asymptomatic hip joints on arthroscopy. ⁵⁷ , ⁵⁸ A positive FADIR test, which is reproduction of groin pain when the hip is placed in a Flexed, Adducted and Internally Rotated position, is commonly used in physical exam for FAI. ⁴⁹ The FADIR test's sensitivity ranges between 0.40 and 0.60, and specificity between 0.47 and 0.52 depending on FAI lesion type. ⁵⁹ Given that FAI is a bony abnormality, plain radiographs of the hips and pelvis with Dunn views (femoral neck x‐rays taken at 45 and 90 degrees) are recommended as best practice for diagnosing FAI. ⁴⁹ , ⁵⁵ , ⁶⁰

4.1.5. Athletic pubalgia

Athletic pubalgia generally presents in young adult athletes as groin or lower abdominal pain with activity. ⁶¹ The pain can radiate to the medial thigh or other regions, thus mimicking L1 and other lumbosacral radiculopathies. ⁶¹ , ⁶² Symptoms are typically unilateral to start but can progress to bilateral. ⁶¹ The underlying pathology is insertional tendinopathy of the adductors and rectus abdominis. ⁶¹

There is a paucity of evidence‐based literature around physical exam findings for this condition, but tenderness around the pubic tubercles, tenderness along the insertion of rectus abdominis and origin of the adductors, and pain with resisted hip adduction or sit‐ups are generally recommended physical exam maneuvers. ⁴⁹ , ⁶³

MRI is the best imaging modality available, with a sensitivity and specificity of 0.68 and 1, respectively, for rectus abdominis tendinopathy and 0.86 and 0.89, respectively, for adductor tendinopathy when compared to surgical findings. ⁶⁴

4.2. L2 radiculopathy mimics

4.2.1. Stress and atypical femoral fractures

Young people engaging in repeated weightbearing exercises can develop femoral neck or femoral shaft stress fractures, whereas the elderly on bisphosphates with no or minimal trauma to the region can develop atypical femoral fractures. ⁴⁹ , ⁶⁵ These fractures can all cause groin and/or thigh pain that is insidious and poorly localized, thus mimicking lumbar radiculopathies. ⁴⁹ , ⁶⁶ , ⁶⁷ Missed diagnosis can lead incomplete, non‐displaced fractures to become complete and displaced, resulting in prolonged hospitalization and higher rates of complications such as non‐union and AVN. ⁶⁸ , ⁶⁹

When compared to lumbar radiculopathies, stress and atypical fractures have a clearer pattern of increased pain during weightbearing. ⁷⁰ Physical exam may show localized tenderness and pain in the thigh and/or at the extremes of ROM. ⁴⁹ , ⁷¹ The hop test can be used for those physically able to perform it to aid in the diagnosis of a femoral fracture: a positive result is pain replication with hopping on the affected leg. ⁷² The fulcrum test can be used for femoral shaft fractures, and involves using the examiner's arm as a fulcrum at multiple locations proximal to distal on the thigh, as force is applied distally to detect pain associated with the fracture. ⁷² , ⁷³ Both tests had 100% sensitivity in a small case series of patients with confirmed femoral stress fractures.

Initial radiographs may be normal, as the sensitivity of x‐rays for lower limb stress fractures can be as low as 0.12. ⁷⁴ MRI is the preferred imaging modality for accuracy, particularly for patients with risk factors such as bisphosphonate use or young female athletes with the triad of disordered eating, menstrual dysfunction and decreased bone density (now termed relative energy deficiency in sport). ⁷⁰ , ⁷⁴ , ⁷⁵ , ⁷⁶ Dual‐energy x‐ray absorptiometry (DXA) is an emerging modality for the evaluation of suspected bisphosphonate‐associated atypical femoral fractures. ⁷⁷

4.2.2. Conditions involving the iliopsoas

The iliopsoas muscle can be affected by painful conditions such as tendinopathy and bursitis that can mimic radiculopathy. ⁷⁸ The iliopsoas bursa communicates with the hip joint, so any intraarticular pathology such as OA or inflammatory arthritis can lead to bursitis. ⁷⁹ Symptoms include anterior hip or groin pain that can be vaguely localized. ⁴⁹ , ⁷⁹ Some patients report a snapping sensation due to the tendon rubbing over the iliopectineal eminence and lesser trochanter with hip ROM, or may notice an inguinal mass due to enlargement of the bursa. ⁴⁹ , ⁷⁹

Evidence based physical exam maneuvers are lacking; physical exam findings that identify the iliopsoas as the source of pain include tenderness to palpation over the iliopsoas, and pain or tightness with the Thomas test or the modified Thomas test. ⁴⁹ , ⁷⁹ , ⁸⁰

Ultrasound (US), MRI, and US‐guided diagnostic injections can be used to confirm the diagnosis. ⁸¹ , ⁸² MRI is recommended as the most accurate imaging modality with the best correlation with surgical findings such as bursa size, but US is an acceptable alternative, based on the results of one study. ⁸¹ , ⁸²

4.3. L3 radiculopathy mimics

4.3.1. Greater trochanteric pain syndrome

Greater trochanteric pain syndrome, previously termed (greater) trochanteric bursitis, is among the most common lower extremity musculoskeletal pain conditions, estimated to affect 10%–25% of the population. ⁸³ Lateral hip pain in proximity to the greater trochanter was classically attributed to trochanteric bursitis, putative inflammation of one or more of the regional bursae. ⁸⁴ However, more recent conceptions of GTPS consider it as a constellation of symptoms involving numerous structures including the trochanteric bursae, gluteus medius, and other regional muscles/tendons. ⁸⁵ GTPS can affect persons of any age, more commonly affects women than men, and frequently occurs concurrently with other musculoskeletal conditions. ⁸⁵ For instance, some studies estimate 20%–35% of persons with chronic low back pain have concurrent GTPS. ⁸³ In one study, GTPS was present in 18% of patients referred for lumbosacral radiculopathy. ⁵

GTPS can be difficult to distinguish from radiculopathies for several reasons. First, the distribution of pain may approximate L3, L4, or L5 radiculopathies due to the common complaint of pain radiating along the lateral thigh in a distal fashion. ⁸³ , ⁸⁶ Second, patients with GTPS often have history and physical examination findings also found in radiculopathy, such as pain in the thigh (58%), pain below the knee (67%), and ipsilateral lower extremity weakness (62%). ⁸⁷ Finally, patients with radiculopathy are at an increased risk of GTPS due to biomechanical alterations, such as Trendelenberg gait, and patients with painful lower extremity conditions are at increased risk of lumbosacral radiculopathy due to imbalances in the spine. ⁸⁸ Biomechanical alterations associated with gluteus medius weakness can lead to GTPS, so clinicians should strongly consider the possibility that GTPS may occur concurrently with L5/S1 radiculopathy.

GTPS is characterized by pain at the lateral hip which may radiate down the lateral thigh, point tenderness at the greater trochanter (Figure 2) with palpation or lying on the affected side, pain with resisted hip abduction in side‐lying, and lateral hip pain at end‐range motion for hip Flexion, ABduction, and External Rotation (i.e., the FABER test, sometimes termed Patrick's test). ⁸³ , ⁸⁵ , ⁸⁹ Ober's test, in which patients lie in lateral decubitus with the affected side up while the examiner passively abducts and extends the hip, and lowers the leg slowly to its passive resting position, is frequently used in the evaluation of patients with suspected GTPS. ⁹⁰ However, studies cast doubt on the utility of Ober's test and the modified Ober's test for this diagnosis. ⁸⁹ , ⁹¹ , ⁹² Pain may also occur with activity, prolonged standing, and transitions from sitting to standing. ⁸³ The onset of pain may be insidious, secondary to biomechanical alterations such as Trendelenberg gait or post‐hip arthroplasty, or may be traumatic, such as after a fall. ⁸⁵

Although the diagnosis is clinical and imaging is rarely required, plain radiographs may be useful to evaluate for other or concurrent conditions such as hip OA; US can be used to identify inflammation of the bursae around the greater trochanter if the diagnosis is in doubt; and MRI can be used to confirm the diagnosis if in doubt or to aid with surgical planning in cases refractory to non‐surgical management. ⁸⁵ , ⁹³ While physiotherapy is a mainstay of treatment and should focus on individualized rehabilitation of the contributing factors, such as hip abductor weakness, a peri‐trochanteric corticosteroid injection can be highly efficacious for treating pain from GTPS, suggesting that a lack of response should lead the clinician to strongly consider alternative diagnoses. ⁹² , ⁹⁴

4.3.2. Iliotibial band syndrome

Iliotibial (IT) band syndrome is characterized by lateral knee pain in individuals who engage in physically strenuous activity, such as running or cycling. ⁹⁵ A leading pathoanatomic explanation is that the IT band rubs over the lateral femoral condyle during repetitive knee flexion and extension. ⁹⁶ The IT band is a complex fibrous structure that arises out of the fascia of the tensor fascia lata muscle at the lateral hip, extends down the lateral thigh, and inserts at Gerdy's tubercle on the lateral tibia. ⁹⁷ Together with the tensor fascia lata muscle, the IT band's primary function is to stabilize the hip and knee in stance phase and assist in hip extension, abduction, and external rotation; at the knee, the IT band also provides lateral stability and resists torsional movements. ⁹⁷ , ⁹⁸ This condition may occur in up to 10% of running and cycling athletes, and is often worse when running downhill. ⁹⁸

IT band syndrome typically presents as activity‐related pain at the lateral knee, proximal to the lateral tibiofemoral joint line, where the band crosses the lateral femoral condyle, but may present with pain that radiates down the lateral thigh, and may therefore be confused for radiculopathy. ⁹⁸ The Noble compression test, which is positive with tenderness over the lateral femoral condyle with passive knee extension to 30 degrees, is a provocative physical exam maneuver that may aid in confirming the diagnosis, which is made clinically. ⁹⁵ , ⁹⁸ The utility of other clinical exam maneuvers, such as the Ober and modified Ober tests, as well as imaging techniques, is controversial. ⁹⁷ , ⁹⁸ IT band syndrome is a clinical diagnosis and imaging, typically dynamic US, is reserved for recalcitrant cases. ⁹⁹

4.3.3. Coxa saltans

The sine qua non of snapping hip, also known as coxa saltans, is the sensation of an audible or palpable snap with hip movement, which is sometimes but not always associated with pain. ¹⁰⁰ Snapping hip is categorized as intraarticular and extraarticular. Extraarticular snapping hip is further categorized to internal and external snapping hip. ¹⁰¹ External snapping hip is most commonly related to the slippage of the IT band or the gluteus medius tendon over the greater trochanter; because it can cause lateral hip pain, it can also be confused with lumbosacral radiculopathy. ¹⁰¹ , ¹⁰² This condition may occur concurrently with GTPS. Like GTPS, coxa saltans is a clinical diagnosis but dynamic US can visualize snapping of the responsible anatomic structures in real‐time and can reveal thickening of the IT band. ¹⁰³

4.4. L4 radiculopathy mimics

4.4.1. Quadriceps muscle contusions or strains

Quadriceps contusion, strain, or conceivably tendon rupture could mimic lumbar radiculopathy based on knee extension weakness and/or the localization of pain in the anterior thigh. ¹⁰⁴ Quadriceps strains commonly occur at the musculotendinous junction at the distal anterior thigh, where there may be palpation tenderness, and typically occur as a result of forceful and often eccentric loads. ¹⁰⁵ Contusions are often associated with a direct trauma with hard objects, such as with sports injuries. ¹⁰⁵ In patients with quadriceps strains, pain can often be produced with active or passive lengthening of the quadriceps muscles by knee flexion or hip extension. In patients with quadriceps contusions, pain is typically worsened with knee flexion and there is often a palpable protuberance and tenderness at the site of contusion. Symptoms with both conditions can be aggravated by weightbearing and ambulation, which can be contrasted with lumbar radiculopathy. The presence of bruising should also lead the clinician to favor the diagnosis of quadriceps musculotendinous pathology over radiculopathy. The diagnosis is clinical but can be confirmed with US or MRI. ¹⁰⁵

4.4.2. Knee osteoarthritis

Knee OA is highly prevalent especially with advancing age. ¹⁰⁶ Approximately one in eight adults ≥55 years of age experience knee pain attributable to knee OA. ¹⁰⁷ The clinical history is often described as slowly progressive non‐radiating whole knee pain that is worse with walking and weightbearing and improved with rest. ¹⁰⁷ Patients with knee OA may report knee instability or weakness, which may also be present on examination. ¹⁵ , ¹⁶ By history, knee pain worse with use has a sensitivity of 0.95 and a specificity of 0.19. ¹⁰⁷

Typical examination findings include bony enlargement (sensitivity 0.55, specificity 0.95), joint line tenderness, malalignment (e.g., varus or valgus), crepitus with ROM (sensitivity 0.89, specificity 0.60), and restricted range of motion, especially knee flexion (sensitivity 0.17, specificity 0.96). ¹⁰⁷ , ¹⁰⁸ It is important for the clinician to also assess passive range of motion of the hip given the well‐known yet often overlooked phenomenon of hip OA with pain that localizes to the knee rather than the hip itself. ¹⁰⁹

Plain radiographs can confirm the diagnosis, assign severity, and offers clinicians guidance on expected symptom progression. ¹⁰⁸

4.5. L5 radiculopathy mimics

4.5.1. Piriformis syndrome

Piriformis syndrome, sometimes termed deep gluteal syndrome, refers to buttock and/or leg pain caused by impingement of the sciatic nerve by the piriformis muscle where the muscle crosses the sciatic notch, coinciding with where the sciatic nerve exits the pelvis. ¹¹⁰ , ¹¹¹ This diagnosis is somewhat controversial and its prevalence is debated. In one prospective study, more than 6% of patients presenting with “sciatica” and low back or buttock pain had piriformis syndrome. ¹¹² In studies examining patients with piriformis syndrome, 35%–100% of patients with this condition had radiation of symptoms to the leg, mimicking radiculopathy. ¹¹⁰ Importantly, the supine straight leg raise test, frequently used in radiculopathy, is often positive in persons with piriformis syndrome. ¹¹³

Patients with piriformis syndrome report buttock and/or radicular pain that is often worse with sitting and with increased tension on the piriformis muscle. ¹¹⁰ Reproduction of buttock and/or leg symptoms using physical exam maneuvers that increase tension on the piriformis muscle, such as passive hip internal rotation and adduction with the hip flexed (the FAIR test) and resisted hip abduction with the hip flexed, support the diagnosis. ¹¹⁰ , ¹¹¹ For instance, the active piriformis test, in which patients lie on the contralateral side and tension the piriformis muscle by abducting and externally rotating their hip while the examiner resists these movements has a sensitivity of 0.78 and specificity of 0.80. ¹¹³ In the passive (seated) piriformis test, tension on the piriformis muscle is generated by having the patient sit with the hip flexed to 90 degrees with the knee in extension, and having the examiner move the hip in adduction and internal rotation while palpating the sciatic notch; this test has a sensitivity of 0.53 and a specificity of 0.90 for piriformis syndrome. ¹¹³ The combination of these two tests improves the sensitivity to 0.91 and specificity to 0.80. ¹¹¹ Tenderness to palpation and/or reproduction of symptoms on palpation of the sciatic notch (Figure 2) is also suggestive of piriformis syndrome. ¹¹⁰

Although most patients with clinical piriformis syndrome do not have EDX abnormalities, and EDX is useful to exclude radiculopathy, the presence of abnormal EDX does not exclude piriformis syndrome. ¹¹¹ In some cases of piriformis syndrome, the sciatic nerve is “entrapped” by the piriformis muscle, producing an axonal sciatic neuropathy with symptoms involving the motor and sensory functions of the sciatic nerve. ¹¹⁴ Whether or not the use of provocative maneuvers exacerbates this entrapment to produce dynamic abnormalities on EDX is controversial. In one study, performing H‐reflex testing with the patient positioned in hip adduction, hip internal rotation, and 90 degrees of hip flexion and finding H‐reflex onset ≥3 standard deviations slower than normal had a sensitivity of 0.88 and specificity of 0.83 for piriformis syndrome. ¹¹⁵ However, other studies have failed to confirm the value of positional H‐reflexes in diagnosing piriformis syndrome, and some experts question whether such an observation is plausible. ¹¹⁶ , ¹¹⁷ Given the poor reliability of many of the above diagnostic tests, confirming the diagnosis of piriformis syndrome may require imaging, such as ultrasound or MRI, and diagnostic and/or therapeutic (image‐guided) injection in the body of the piriformis muscle with corticosteroids or botulinum toxin. ¹¹⁸ , ¹¹⁹ , ¹²⁰

4.5.2. Exertional compartment syndrome

One of many conditions under the umbrella of exercise‐induced leg pain, exertional compartment syndrome presents with pain in any of the four compartments of the leg (anterior, lateral, superficial or deep posterior) that comes on with activity and resolves or dramatically diminishes after a period of rest that is typically reproducible within an individual but may vary between individuals. ¹²¹ The incidence is estimated at one per 2000 persons per year and often occurs in runners and other highly active persons. ¹²² Patients affected by exertional compartment syndrome often have no risk factors for vascular or neurogenic claudication, although there is significant symptom overlap given the exertional nature of this condition. ¹²¹ , ¹²² In older and/or diabetic patients presenting with these features, further workup to exclude peripheral vascular disease and vascular claudication may be warranted. ¹²³ Additional symptoms, estimated to affect one in three patients with exertional compartment syndrome, may include weakness, cramps, and/or paraesthesiae or hypoesthesiae in one or more peripheral nerves of the leg, and may therefore be mistaken for radiculopathy. ¹²¹ , ¹²⁴ Symptoms are often but not always symmetric and start reproducibly at the same intensity, duration, and/or distance of exercise. Physical examination and electrodiagnostic testing (if undertaken) are typically normal. ¹²¹ Diagnosis can be made with specialized testing with dynamic intra‐compartmental pressure monitoring during exercise. ¹²²

4.5.3. Tibial and/or fibular stress syndrome

These diagnoses also fall under the umbrella of exercise‐induced leg pain, and typically present with leg pain onset with running, most often at the medial tibia (medial tibial stress syndrome). ¹²¹ A condition of many names, such as periostitis and shin splints, the pathophysiology is thought to arise from reaction of bone to repetitive loading. ¹²⁵ Medial tibial stress syndrome is among the most common conditions affecting runners and running athletes, with an estimated incidence up to 34% and prevalence more than 9% in this population. ¹²¹ , ¹²⁵ In contrast to exertional compartment syndrome, the pain of tibial and/or fibular stress syndrome often persists for hours to days after cessation of exercise and may be reproduced on physical examination with palpation along the affected bone(s), such as at the medial tibial border, typically exquisitely tender over a span ≥5 cm in length. ¹²⁵ Because of the lingering nature of pain and its distribution, it may be mistaken for radiculopathy. The diagnosis is primarily clinical, but to rule out stress fracture, plain x‐rays are often sufficient. ¹²⁵ However, if required for diagnosis and/or severity grading, MRI can be used. ¹²⁵

4.6. S1 radiculopathy mimics

4.6.1. Hamstring strains and proximal hamstring tendinopathy

The hamstrings consist of three muscles, semimembranosus, semitendinosus, and biceps femoris, that collectively flex the knee and extend the hip. These muscles are vulnerable to both sudden injury or insidious, degenerative tendinopathy, particularly proximally at the ischial tuberosity. ¹²⁶ In hamstring conditions of acute and/or insidious onset, pain can radiate, often to the popliteal fossa, and patients may have knee flexion weakness, both mimicking radiculopathy. ¹²⁷ , ¹²⁸ Acute hamstring injuries tend to arise from eccentric loading, such as sprinting to first base in baseball, or movements of extreme hip flexion and knee extension, like kicking. ¹²⁷ Patients who present with hamstring strains and/or acute tears typically report sudden onset of posterior thigh pain; they may have bruising and/or a palpable defect within the muscle belly. ¹²⁸ Patients who develop proximal hamstring tendinopathy frequently present with insidious onset of buttock and posterior thigh pain, which may radiate to the popliteal fossa. ¹²⁸ Pain may localize to and be reproducible on palpation of the proximal hamstring attachment at the ischial tuberosity but these patients usually do not have a palpable defect in the muscle belly. ¹²⁸ Patients with hamstring muscle or tendon pathology may have weakness of knee flexion, walk with a stiff‐knee gait to avoid terminal knee extension and eccentric hamstring activation, and have pain reproduced with hamstring stretch. ¹²⁸ Pain with resisted knee flexion and pain with rapid passive knee extension from a flexed position are common features on provocative testing. ¹²⁶ , ¹²⁸ Positive findings on active resisted knee flexion with the knee at 30 and 90 degrees of flexion have a specificity of 0.97 and a positive likelihood ratio of 26.9 in one study of patients without “sciatica.” ¹²⁹ Diagnosis can be confirmed with US and/or MRI if needed to support clinical decision‐making. ¹²⁶ , ¹³⁰

4.6.2. Ischiofemoral impingement

In this condition, patients experience pain arising from compression of the quadratus femoris muscle between the ischial tuberosity and the lesser trochanter of femur. ¹³¹ Clinically, patients present with gradual onset of posterior and/or posteromedial buttock pain with or without radiation to the posterior thigh that is worse with hip extension, adduction, and external rotation. ¹³¹ A positive long stride walking test is supportive of the diagnosis. ¹³⁰ , ¹³² MRI to evaluate for signs of focal edema in the quadratus femoris muscle can aid in diagnosis. ¹³²

4.6.3. Ischiogluteal bursitis

Often termed a “pain in the arse” for its clinical symptoms and difficulty to diagnose, ischiogluteal bursitis presents with central buttock pain that radiates down the posterior thigh. ¹³³ The precise epidemiology is unknown. Experts have long opined that ischiogluteal bursitis, also referred to as weavers' bottom, is rare but likely underdiagnosed, in part because it is easily confused for a variety of other conditions, including soft tissue tumors and radiculopathy. ¹³³ , ¹³⁴ , ¹³⁵ , ¹³⁶ Ischiogluteal bursitis refers to inflammation of the ischial bursa, which lies between the ischial tuberosity and gluteus maximus muscle in standing, and between the ischial tuberosity and the skin in sitting. ¹³⁷ , ¹³⁸

On history, patients may report pain that is excruciating when sitting and patients may report being unable to sit. ¹³⁵ Ischiogluteal bursitis develops at the ischial tuberosity, where the hamstring tendons originate, and so patients may also report pain with actions that involve hamstring contraction, such as running, jumping, or kicking. ¹³⁵ On physical examination, the vast majority of patients will present with pain reproducible by palpating the ischial tuberosity (Figure 2). ¹³⁹ Diagnosis may be difficult to make clinically, and experts advocate for image‐guided diagnostic/therapeutic injection, US, or MRI to improve diagnostic accuracy. ¹³⁵ , ¹³⁹

4.6.4. Sacroiliac joint pain and dysfunction

The sacroiliac joint (SIJ) is the largest axial joint and consists of a synovial joint and complex ligamentous structures. SIJ dysfunction is a common cause of low back, buttock, and leg pain, with a prevalence of 15%–30% in persons presenting with low back pain. ¹⁴⁰ Although the sacroiliac joint is located in the posterior pelvis, pain arising from the joint can manifest as pain in the lumbar spine, buttock, leg distal to the knee, and into the foot. ¹⁴¹ The pain tends to worsen with transitions, such as from sitting to standing. ¹⁴⁰ Numerous provocative tests have been described. ¹⁴² Pain to palpation of the SIJ (just inferior and medial to the posterior superior iliac spine) and absence of pain above L5 support the diagnosis. ¹⁴⁰ Additional evidence‐based tests include Gaenslen's test, SIJ distraction test, thigh thrust test, SIJ compression test, and the FABER test, although none of these tests have high reliability when used alone. ¹⁴⁰ , ¹⁴² Due to the challenging nature of the diagnosis, some experts advocate that the presence of three positive tests should be considered indicative of SIJ dysfunction (sensitivity 0.94, specificity 0.78). ¹⁴⁰ , ¹⁴³ , ¹⁴⁴ Injection into the SIJ can also provide diagnostic and/or therapeutic benefit and confirm the diagnosis. ¹⁴⁵ , ¹⁴⁶

Although inflammatory arthritides and spondyloarthropathies may present with SIJ pain, a comprehensive review of relevant history and physical examination findings is beyond the scope of this review. However, clinicians should strongly consider the possibility in patients with skin or nail manifestations of psoriasis, a personal history of uveitis or inflammatory bowel disease, a family history of spondyloarthropathy, or clinical dactylitis. ¹⁴⁷

4.6.5. Plantar fasciitis

Plantar fasciitis, also termed plantar fasciopathy due to the absence of inflammation in this condition, is estimated to affect one in 10 persons in their lifetime, making it among the most common musculoskeletal conditions. ¹⁴⁸ In one study, PF was present in 5% of patients referred for evaluation of lumbosacral radiculopathy. ⁵ PF affects active and sedentary adults of all ages, and presents with plantar surface heel pain. ¹⁴⁸ PF is an overuse and degenerative condition involving the plantar fascia at its attachment to the calcaneus. ¹⁴⁸ Risk factors for the development of PF include high body mass index, professions involving prolonged standing, high and/or low medial longitudinal arches (pes cavus or planus), altered ankle biomechanics, and excessive running. ¹⁴⁸ On physical examination, tenderness to palpation at the anteromedial plantar calcaneus and/or a positive Windlass test (heel pain with passive forced dorsiflexion of the metatarsophalangeal joints) (sensitivity 0.32, specificity 1), help confirm the diagnosis. ¹⁴⁹ PF often does not require imaging; however, in cases that persist despite appropriate treatment, plain radiographs (looking for a calcaneal heel spur) and/or ultrasound (looking for thickened and/or abnormal fascial tissue) may be helpful. ¹⁴⁸ , ¹⁴⁹ , ¹⁵⁰

4.7. S2‐4 radiculopathy mimics

Conditions in this section are among the most challenging to diagnose, even for experienced specialists in musculoskeletal conditions, and may therefore be underrecognized radiculopathy mimics. ¹⁵¹

4.7.1. Gemelli–obturator internus syndrome

The superior and inferior gemelli along with obturator internus, which are external rotators of the hip, form a conjoint tendon known as triceps coxae, which inserts into the greater trochanter between piriformis superiorly and quadratus femoris inferiorly. ¹⁵² The putative pathoanatomic explanation for gemelli–obturator syndrome is compression of the sciatic nerve as it emerges from deep to piriformis and courses superficial to the gemelli–obturator complex due to stretching of the latter muscle group. ¹⁵³ This theory is supported by a study demonstrating curvature of the sciatic nerve resulting from the stretch of the gemelli and obturator internus with hip internal rotation as demonstrated with dynamic ultrasound in cadavers and healthy volunteers. ¹⁵⁴ Gemelli–obturator internus syndrome is thought to result in retro‐trochanteric pain, which could be confused with lower sacral radiculopathy. ¹⁵⁵ The clinician suspecting the presence of this syndrome should assess for a reproduction of symptoms with passive internal rotation of the hip. The imaging modality of choice is MRI. ¹⁵²

4.7.2. Coccydynia

Coccydynia, or coccyx/tailbone pain, more commonly affects women than men and has many potential etiologies, including idiopathic and traumatic causes like coccyx fracture. ¹⁵⁶ , ¹⁵⁷ , ¹⁵⁸ Although a rare diagnosis, estimated to account for 1% of nontraumatic axial spine pain, coccydynia warrants mention because of its potentially disabling nature and the specific investigations and management required. ¹⁵⁷ , ¹⁵⁸ While usually considered non‐neurogenic in origin, pain in the region of the coccyx may arise from compression of lower spinal nerve roots. ¹⁵⁷ Coccydynia is characterized by pain and tenderness of the lower sacrum at the site of the coccyx or sacrococcygeal articulation. ¹⁵⁷ Patients may report pain that worsens with prolonged sitting, pain with sexual intercourse (dyspareunia), and pain with defecation (dyschezia). ¹⁵⁷ Imaging should include dynamic plain films with standing and sitting views that can reveal pathologic motion. ¹⁵⁹ A favorable response to interventional pain treatment would support coccyx pain over lower sacral radiculopathy.

4.8. Other mimics of radiculopathy

4.8.1. Myofascial pain syndrome

Although there is incomplete consensus, one definition of myofascial pain is pain originating from an exquisitely tender, taut muscular band within skeletal muscle that reproduces the patient's pain experience. ¹⁶⁰ , ¹⁶¹ It is often observed in regional pain syndromes and features radiation of pain that can mimic radiculopathy. ⁷ , ¹⁶² In one study of patients referred for suspected lumbosacral radiculopathy, 20% of patients had myofascial pain. ⁵ The hallmark of myofascial pain is a subjective pain resulting from firm manual pressure over bands of muscle fibers by the clinician. ¹⁶³ There are several described myofascial referral patterns encompassing several dermatomal territories of the lower extremities and myofascial pain often results in paresthesiae and dysesthesiae in anatomic regions that are remote from the site of trigger points. ¹⁶⁴ , ¹⁶⁵ , ¹⁶⁶ Myofascial pain can therefore mimic radiculopathy arising from multiple root levels. ¹⁶⁷ There is indeed high prevalence of myofascial pain among patients referred for electrodiagnostic studies and myofascial pain is much more common in individuals with normal studies than those with electrodiagnostically proven dysfunction of the peripheral nervous system. ⁵ There are no specific “special tests” that can be used to diagnose myofascial pain. The use of diagnostic imaging such as ultrasound has been described for the evaluation of myofascial pain syndrome and accompanying myofascial trigger points but, in the authors' experience, has yet to be adopted widely into clinical practice, in part due to limited evidence. ¹⁶⁸

4.8.2. Mechanical low back pain, lumbar facet syndrome, and interspinous ligament pain

Lumbar facet syndrome, also known as lumbar zygapophyseal joint arthropathy, and degenerative changes to the interspinous ligaments, among other anatomical structures, are common causes of chronic low back pain, often intimately associated with degenerative disc disease and other cumulative, degenerative conditions of the axial spine. ¹⁹ , ¹⁶⁹ As with all of the conditions discussed in this review, the lumbar facet joints and interspinous ligaments can produce referred pain, including to the groin, flank, hip, upper and lower lateral thigh, posterior thigh, lower lateral leg, and foot (Figure 3) ¹⁶⁹ ; Pain is usually insidious in onset without a single clear inciting event. Physical exam maneuvers have low reliability but positive features may include pain worse with forward flexion or lumbar extension and/or extension/rotation maneuvers, and pain on palpation of the paraspinal muscles. ¹⁷⁰ , ¹⁷¹ , ¹⁷² Diagnostic clarification and therapeutic benefit may arise from facet joint injections and/or medial branch blocks followed by radiofrequency ablation. ¹⁹ , ¹⁷² , ¹⁷³ , ¹⁷⁴

FIGURE 3.

Patterns of referred pain from lumbosacral interspinous ligaments. Referred pain from conditions affecting the low back may be mistaken for radiculopathy. For instance, pain generated by lumbosacral interspinous ligaments frequently presents in the patterns outlined above, and therefore can mimic lumbosacral radiculopathy. Source: Adapted with permission from Kellgren. ¹³

5. DISCUSSION

The differential diagnosis for lumbosacral radiculopathy is broad, as multiple structures and conditions can produce back and lower extremity pain, including non‐radiculopathy disorders of the peripheral nervous system, disorders of the central nervous system, and musculoskeletal disorders. ⁵ , ⁷ Musculoskeletal disorders, the focus of this review, can mimic and/or occur concurrently with lumbosacral radiculopathy. As summarized in the Introduction, the prevalence of lumbosacral radiculopathy is lower than that of common MSK disorders such as great trochanteric pain syndrome.

The ability to correctly identify radiculopathy with or without other concurrent musculoskeletal diagnoses is challenging. Because of the high prevalence of other disorders seen in patients referred for EDX for lumbosacral radiculopathy, a solid working knowledge of high‐yield examination maneuvers can improve patient satisfaction and promote resource stewardship. ⁵ Referrals to MSK disorder specialists should also be considered when the electrodiagnostic medicine specialist who does not practice MSK medicine suspects a MSK disorder mimic.

6. CONCLUSION

Musculoskeletal disorders are common in patients referred to electrodiagnostic medicine specialists. Not all pain that radiates to the buttock, thigh, leg, or foot arises from compression of one or more lumbosacral spinal nerve root(s). Recognition of musculoskeletal disorders that may mimic radiculopathy is important to avoid unnecessary diagnostic testing, potentially inappropriate invasive procedures, and to improve patient care and satisfaction.

AUTHOR CONTRIBUTIONS

All authors contributed equally to this work.

ETHICS STATEMENT

We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.

Bateman EA, Fortin CD, Guo M. Musculoskeletal mimics of lumbosacral radiculopathy. Muscle & Nerve. 2025;71(5):816‐832. doi: 10.1002/mus.28106

DATA AVAILABILITY STATEMENT

Data sharing not applicable no new data generated, or the article describes entirely theoretical research.