Is My Pain Coming From My Lumbar Spine, Hip, or Sacroiliac Joint?

All information in this blog is supported by NICE guidelines and peer-reviewed research. Reference numbers appear throughout, with the full list at the bottom of the page.

Have You Been Given Different Answers by Different Clinicians?

You have pain somewhere around your lower back, hip, buttock, groin, or thigh. You may have seen your GP, a physiotherapist, or a consultant, and been given a different explanation by each one. Or perhaps you've been told it's your back, but your pain feels like it's in your hip. Or you've been told it's your hip, but it started in your lower back.

This is genuinely one of the most common and most frustrating experiences people have when seeking help for lower body pain, and it isn't a failure of any individual clinician. The lumbar spine, the hip joint, and the sacroiliac joint (SIJ) are three distinct structures that share overlapping nerve supply, produce overlapping referral patterns, and can all coexist in the same person simultaneously. Even the most experienced practitioners need a structured, systematic assessment to reliably tell them apart, and research confirms that pain location alone is simply not enough to make an accurate diagnosis. ¹

This blog is designed to help you understand the differences between these three sources of pain, where each one refers to, and how a thorough assessment can help identify the true origin of your symptoms.

Why Is This So Confusing?

The fundamental reason these three conditions are so difficult to distinguish is that they all share the same nervous system territory. Sclerotomal pain, pain arising from bones, ligaments, and joints, is characteristically deep, diffuse, and poorly localised, meaning the brain struggles to accurately identify exactly where it is coming from. ² This variability complicates diagnosis considerably and underscores the need for a structured, regional assessment approach rather than relying on pain location alone. ²

A striking research finding puts this into perspective: the lumbar spine accounts for 88 to 90% of all cases where patients present with pain in the SIJ region, yet the SIJ itself is only the primary pain generator in 3 to 6% of those same cases. ³ This means that pain felt in what seems like the SIJ area is actually coming from the lumbar spine in the vast majority of people, a finding that genuinely changes how assessment should be approached.

Further complicating the picture is the concept of hip-spine syndrome, where concurrent pathology in both the hip joint and the lumbar spine coexists in the same person, creating overlapping and shifting symptoms that can make confident diagnosis exceptionally challenging without systematic evaluation. ⁴

NICE guideline NG59, Low Back Pain and Sciatica in Over 16s: Assessment and Management, is explicit that a thorough assessment should be carried out at the first point of contact to identify the likely source of symptoms and exclude serious pathology before treatment begins. ⁵

Lumbar Spine Referral Patterns

The lumbar spine has eight potential nerve root levels contributing to lower limb sensation and movement, and each one has a broadly predictable referral zone. Understanding this helps explain why lower back pathology can produce pain felt entirely in the groin, thigh, calf, or foot with little or no back pain at all.

L1: upper groin, lower abdomen, and upper anterior thigh. Pain here can mimic hip flexor or groin pathology very convincingly.

L2: anterior and medial thigh, groin. The L2 spinal nerve provides sensation to the front of the thigh and the groin region, and irritation here is one of the most commonly missed causes of anterior thigh pain. ⁶

L3: anterior thigh, front of the knee, medial lower leg, and inner calf. Research has found this level is commonly affected by disc pathology and produces pain that extends from the back down to the inner knee and calf. ⁶ Loss of the knee jerk reflex may be present in more significant compression.

L4: lateral and anterior thigh, medial shin, inner ankle, and the big toe area. The L4 dermatome runs from the midline of the trunk, across the buttock, through the lateral and anterior thigh, and down the medial side of the lower leg to the first toe. ⁷ Reduced or absent knee jerk reflex is a useful clinical indicator of L4 involvement.

L5: lateral calf, top of the foot, and the first and second toes. L5 is the most frequently involved level in lumbar disc herniation, and difficulty lifting the foot (foot drop in severe cases) is a classic sign of significant L5 nerve root compression. ⁷ The L5 dermatome extends from the posterior trunk, through the buttock, down the posterior and lateral aspect of the thigh and leg, to the fifth toe.

S1: posterior thigh, lateral foot, little toe, sole, and heel. Loss of the Achilles reflex is the most useful clinical indicator of S1 involvement. The S1 dermatome spans the posterior thigh, lateral foot, and fifth toe, making it essential for evaluating sciatic nerve dysfunction. ⁶

A genuinely important nuance: real-world lumbar referral patterns are frequently inconsistent with the classic textbook dermatomal maps. Research using diagnostic nerve blocks found that the most common referral pattern across L3 to S1 was the buttock, the posterior thigh, and the posterior calf, regardless of the specific level being stimulated. ⁸ Referred pain to the anterior, medial, and lateral thighs does more frequently follow predicted dermatomal maps, but posterior referral is variable and may arise from L3, L4, L5, or S1 all producing similar patterns. ⁸ This is exactly why level-specific diagnosis based on pain location alone is genuinely unreliable in clinical practice.

Clinical Tests for Lumbar Spine Involvement

NICE NG59 recommends a thorough clinical assessment to identify the likely source of symptoms, with imaging not routinely required unless there are specific red flags or the diagnosis remains unclear. ⁵

Straight leg raise (SLR): high sensitivity of around 80 to 90% for L4, L5, and S1 nerve root compression. A positive test reproduces leg pain below the knee when the hip is raised between 30 and 70 degrees of flexion. ⁹

Crossed straight leg raise: lower sensitivity but specificity of around 90% for nerve root compression. Reproduction of the patient's familiar leg pain when raising the unaffected leg is highly suggestive of significant nerve root compression, typically from a disc herniation. ⁹

Femoral nerve stretch test: research has found this test has high sensitivity, reaching 100% in some studies, for upper lumbar nerve root compression at L2, L3, and L4. This is the key test for detecting anterior thigh and groin referral from the upper lumbar spine. ⁹

Slump test: useful for identifying neuropathic lower limb pain, particularly when combined with the SLR to add structural differentiation. ¹⁰

Neurological examination cluster (sensory, motor, and reflex testing): combining all three neurological tests gives the strongest diagnostic picture. Reflex testing has shown the best specificity across studies, with the knee jerk reflex most useful for L3/L4 and the Achilles reflex for S1. Research involving 864 participants found that combining neurodynamic and orthopaedic tests in parallel significantly improved diagnostic accuracy compared to any single test alone. ⁹

Hip Joint Referral Patterns

The hip joint produces a very different and, in many ways, more localised referral pattern compared to the lumbar spine, though the overlap with both lumbar and SIJ pain is still genuinely significant.

Classic hip joint referral: groin and anterior thigh pain are the primary, most consistent referral zones for hip joint pathology. The "C-sign," where the patient cups their hand around the front and side of the hip to describe their pain, is a well-recognised clinical indicator of intra-articular hip joint origin. ⁴

Additional referral sites: the front of the thigh toward the knee, and occasionally into the buttock, though buttock-dominant pain is more commonly lumbar or SIJ in origin. Pain extending to the knee is not uncommon in hip osteoarthritis, and knee pain can genuinely be the initial complaint in someone whose primary problem is at the hip. ⁴

Different hip conditions produce subtly different patterns. Hip osteoarthritis typically produces groin and anterior thigh pain that is worse with weight-bearing activity and rotation of the hip. Labral tears and femoroacetabular impingement (FAI) tend to produce deeper groin pain, often with a catching sensation, worse with sustained hip flexion such as prolonged sitting. Iliopsoas tendinopathy produces anterior hip and groin pain specifically worsened by resisted hip flexion.

Clinical Tests for Hip Joint Pathology

The gold standard for hip osteoarthritis diagnosis is a standing anteroposterior X-ray of the pelvis. A validated clinical prediction rule developed specifically for hip OA (Sutlive et al.) identifies hip OA with a positive likelihood ratio of 24.3 when all five of the following findings are present: squatting aggravates symptoms, active hip flexion causes lateral hip pain, a scour test with adduction causes groin or thigh pain, active hip extension causes pain, and passive internal rotation is 25 degrees or less. ¹¹

FABER test (flexion, abduction, external rotation): a useful indicator of hip joint irritability, often positive in hip OA, labral pathology, and notably also in SIJ dysfunction, reflecting the genuine overlap between these two conditions in clinical presentation. ¹²

FADIR test (flexion, adduction, internal rotation): positive in FAI and labral pathology, reproducing deep groin or anterior hip pain and helping distinguish intra-articular from extra-articular hip sources. ¹²

Passive internal rotation: reduced range below 25 degrees is one of the strongest single clinical indicators of hip joint pathology and forms a core component of the validated hip OA clinical prediction rule. ¹¹

Trendelenburg test: assesses gluteal muscle function and pelvic stability, relevant particularly for identifying greater trochanteric pain syndrome alongside hip joint conditions. ¹²

Sacroiliac Joint Referral Patterns

The SIJ's referral pattern is the widest and most variable of the three, which is exactly why it mimics both lumbar and hip pathology so convincingly.

Buttock: the most consistent and common referral site, present in the vast majority of confirmed SIJ cases. The "Fortin finger sign," where the patient can point to a small area just below and medial to the posterior superior iliac spine (PSIS) with one finger, is the most specific single indicator of SIJ involvement. ¹³

Lower lumbar region: pain just below the waistline on the affected side, which when combined with buttock pain increases clinical suspicion of SIJ involvement over lumbar spine pathology alone.

Posterior thigh: the most common lower limb referral site, occurring in approximately 50% of patients with confirmed SIJ pathology. This is one of the most important reasons SIJ dysfunction gets mistaken for sciatica or lumbar disc herniation. ¹⁴

Groin and anterior thigh: present in around 44% of confirmed SIJ cases, confirmed by diagnostic injection studies showing symptom resolution with SIJ block. This is one of the most commonly missed features of SIJ dysfunction. ³

Lower leg, knee, and foot: less common, but documented referral sites that further extend the overlap with lumbar radiculopathy patterns.

Muscle spasm in the anterior thigh: a genuine and recognised feature of SIJ dysfunction, via the rectus femoris and iliopsoas muscles that have direct anatomical relationships with the SIJ ligaments. Spasm of the iliac muscle specifically has been identified as a mechanism producing groin pain and tenderness in SIJ dysfunction. ¹⁵

Clinical Tests for SIJ Dysfunction

The true gold standard for SIJ diagnosis is a fluoroscopically guided diagnostic nerve block, with 75% or greater pain relief on two occasions confirming the SIJ as the source. In clinical practice, the validated provocation test cluster approach is the most evidence-based option available. ¹⁶

The Laslett cluster (the most widely validated approach): comprising the distraction test, compression test, thigh thrust test, Gaenslen's test, and sacral thrust test. Three or more positive tests from this cluster gives a sensitivity of 88% and a specificity of 78%, making it the strongest available clinical tool for SIJ diagnosis without injection confirmation. ¹⁷

Positive likelihood ratio with three or more positive tests: a meta-analysis reported a positive likelihood ratio of 3.19 for three or more positive provocation tests, meaningfully increasing the probability of a genuine SIJ source. ¹⁷

Distraction test: an anterior distraction force applied to both anterior superior iliac spines, positive when it reproduces the patient's familiar posterior pelvic pain.

Thigh thrust test: a posterior shear force applied through the hip and pelvis with the hip at 90 degrees of flexion, considered one of the most sensitive individual SIJ provocation tests.

Important caveat: no single SIJ provocation test has sufficient diagnostic accuracy on its own. The cluster approach is genuinely essential, and motion palpation tests alone have been shown to have poor diagnostic accuracy. ¹⁶

Comparison Table: Lumbar Spine, Hip, and SIJ

Feature	Lumbar Spine	Hip Joint	Sacroiliac Joint
Primary pain location	Lower back, though sometimes absent	Groin and anterior hip	Posterior pelvis, below the waistline
Key referral zones	Buttock, posterior thigh, lateral or medial leg, foot depending on level. Groin with upper lumbar levels	Anterior thigh, knee, occasionally buttock	Buttock, posterior thigh, groin, anterior thigh, occasionally lower leg and foot
What makes it worse	Sustained flexion, sitting, coughing, sneezing, bending	Weight-bearing, rotation of the hip, prolonged sitting	Asymmetrical pelvic loading, stairs, rolling in bed, rising from sitting
What makes it better	Walking, position change, extension where disc is involved	Rest, avoiding rotation	Lying flat, symmetrical positions
Neurological features	Possible numbness, tingling, weakness, reflex changes depending on level	Rarely neurological unless severe	Occasional numbness and tingling, leg instability
Key clinical clue	Reproduction of leg symptoms with SLR or slump test. Reflex changes	C-sign, reduced passive internal rotation, positive FABER or FADIR	Fortin finger sign, three or more positive Laslett cluster tests
Gold standard	MRI for nerve root compression. Clinical assessment for non-specific pain	Standing AP X-ray for OA. Clinical prediction rule	Fluoroscopic diagnostic nerve block. Laslett cluster clinically
NICE guideline	NG59	NG226 (osteoarthritis)	No dedicated NICE guideline

"Where Is Your Pain?" A Simple Self-Assessment Guidemple Self-Assessment Guide

This is not a diagnostic tool and cannot replace professional assessment. It is designed to help you think about your symptoms before your appointment.

Pain mainly in the groin and front of the thigh: consider hip joint pathology as the most likely source, particularly if rotation of the hip worsens your symptoms. Upper lumbar nerve root referral (L1, L2, L3) is also a genuine possibility. SIJ referral to this area affects around 44% of confirmed SIJ cases and should not be excluded.

Pain mainly in the buttock and back of the thigh: this is the most overlapping pattern of all three conditions. The lumbar spine is the most common source, followed by the SIJ. Hip joint pathology is less likely but possible, particularly in the buttock.

Pain on the outer side of the thigh and lateral leg: strongly suggests L5 nerve root involvement from the lumbar spine. Iliotibial band-related pain is also worth considering.

Pain below the knee into the foot: most likely lumbar nerve root in origin, particularly L4, L5, or S1. SIJ and hip joint referral below the knee is possible but significantly less common.

Pain that is one-sided and stays on the same side: more consistent with SIJ dysfunction or unilateral lumbar radiculopathy. Hip joint pain is also almost always unilateral.

Pain associated with numbness, tingling, or weakness: strongly suggests lumbar nerve root involvement. SIJ dysfunction can produce neurological-type symptoms through its proximity to the lumbosacral plexus, but true weakness is uncommon without lumbar spine involvement.

Pain that is worse specifically with pelvic loading movements such as stairs, standing on one leg, or rolling in bed: raises the suspicion of SIJ dysfunction as a significant contributor.

Why Accurate Diagnosis Matters

Getting this right is not just academic. Treating the wrong structure consistently leads to incomplete or short-lived recovery. Research has consistently found that people with misdiagnosed sources of lower back and hip pain are more likely to follow unnecessary treatment pathways, experience prolonged disability, and develop chronic pain. ¹

NICE NG59 is clear that a thorough assessment should identify the likely source of symptoms before treatment is started, with management decisions based on that assessment rather than on symptom location alone. ⁵ This is exactly why we take the time at your first appointment to work through a structured, systematic examination of all three potential sources rather than simply treating where the pain is felt.

When Should You Be Concerned? Red Flags to Watch For

Please seek urgent medical attention if you experience any of the following alongside your back, hip, or pelvic pain:

• Loss of bladder or bowel control

• Numbness in the inner thighs, groin, or saddle area

• Rapidly worsening weakness in both legs

• Severe pain following significant trauma

• Unexplained weight loss alongside musculoskeletal pain

• Fever or feeling generally unwell alongside joint or back pain

• A visible deformity or inability to bear weight following an injury

NICE NG59 specifically identifies these red flag features as requiring urgent assessment to rule out serious underlying pathology, including cauda equina syndrome, fracture, malignancy, and infection. ⁵

How We Can Help

At our clinic, we approach complex presentations like these with a structured, systematic assessment designed to identify the true source of your symptoms rather than simply treating where the pain is felt. This means assessing all three potential contributors, the lumbar spine, the hip joint, and the SIJ, alongside each other, using validated clinical tests for each structure rather than relying on pain location alone.

We will carry out a full neurological screen where relevant, apply the appropriate test clusters for each condition, and explain clearly what we find in plain language before building a treatment plan targeted at the actual source of your pain.

Frequently Asked Questions

Can I have all three at once? Yes, genuinely. Hip-spine syndrome, where concurrent hip and lumbar spine pathology coexist, is a well-recognised clinical entity, and SIJ dysfunction frequently coexists with mechanical low back pain. Having more than one contributing source is common, particularly in middle-aged and older adults, which is exactly why a thorough assessment of all three is always worthwhile.

Do I need a scan? Not always. NICE NG59 advises against routine imaging for non-specific low back pain, and the clinical prediction rule for hip OA and the Laslett cluster for SIJ can both be applied without imaging. Your practitioner will advise if imaging is appropriate for your specific presentation.

Why does my pain seem to move around or change location? This is genuinely common in sclerotomal referred pain, which is characteristically diffuse and variable. It can also reflect the fact that more than one structure is contributing to your symptoms at different times, or that your pain sensitisation levels are fluctuating, which alters how pain is perceived and localised.

My GP told me it's my back, but the pain is in my hip. Who is right? Both may be. The overlap is genuine and well-documented, and as discussed, lumbar spine pathology accounts for the vast majority of pain that feels like it's in the hip or SIJ region. A thorough hands-on assessment, rather than pain location alone, is what reliably distinguishes between them.

Will a scan tell me which one it is? Not definitively. Imaging shows structural changes but cannot reliably identify the source of pain, since disc degeneration, hip joint changes, and SIJ findings are all common in people without any pain at all. A structured clinical assessment, combined with imaging where appropriate, gives the most accurate overall picture.

Not sure where your pain is coming from? Get in touch using the contact form and we will carry out a thorough, systematic assessment to identify the true source and build the right treatment plan for you.

BOOK YOUR APPOINTMENT HERE

References

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