Every month, patients arrive in a spine clinic carrying an MRI of a degenerative lumbar spine and a hip that has never been examined — and patients arrive in hip clinics with the reverse file. The two conditions are both diseases of the same decades of life. They refer pain into overlapping territory, and they coexist often enough that finding one proves nothing about the other. The clinical error is not ignorance of either disease. It is stopping at the first abnormality found and treating the picture instead of the source.
The sorting is a defined process, built on one principle: pain geography suggests, examination discriminates, imaging confirms only when it agrees with both, and when the case remains uncertain, a diagnostic injection settles what examination and imaging could not. What follows is that process, in the order it is run.
The Problem Has a Name: Hip-Spine Syndrome
Offierski and MacNab described the hip-spine syndrome in 1983 (Spine, 1983) — coexisting hip and lumbar disease in which the symptoms of one mask or mimic the other. Their classification still organizes the workup. In the simple syndrome, one source is symptomatic and the other is silent: an arthritic hip with an aging but painless spine. In the secondary syndrome, one disease drives the other mechanically — a hip that has lost motion develops a flexion contracture, the pelvis tilts to compensate, the lumbar spine is held in increased lordosis, and the back pain that results is real back pain with a hip cause. In the complex syndrome, both are symptomatic and no single finding establishes which predominates; that is the category where the diagnostic injection earns its place.
Why the Two Are Confused
The referral maps overlap almost completely. The hip joint refers pain to the groin, the front of the thigh, the buttock, and occasionally the knee. The lumbar nerve roots refer pain to the buttock, the thigh, and — when a root is truly involved — below the knee in a dermatomal band. Buttock pain, the commonest presenting complaint in both clinics, sits in the intersection and discriminates poorly on its own. Both joints degenerate across the same decades, so the prior probability of an abnormal image is high on both sides. In one study of 388 patients over 50 undergoing spinal surgery, 32.5% had significant hip pathology visible on plain pelvis radiographs (Lee et al., Indian Journal of Orthopaedics, 2012). That figure is radiographic — hips that looked arthritic on film, in a spine-surgery population — and its lesson is narrow and important: in this age group, the second door is loaded often enough that it must be examined, every time.
The Examination: Three Findings Carry the Weight
Brown and colleagues studied 97 consecutive patients presenting mainly with lower-extremity pain and sorted them by their final diagnosis — spine only, hip only, or both (Clinical Orthopaedics and Related Research, 2004). Three findings separated the groups. Patients who limped were seven times more likely to have a hip-only or a combined hip-and-spine source than a spine-only source. Patients with groin pain were seven times more likely to have a hip or combined source. And patients with limited internal rotation of the hip were fourteen times more likely to have a hip or combined source. Those three findings — a limp, groin pain, and a restricted internal rotation arc — are the discriminating core of the examination.
Internal rotation deserves its emphasis. The hip is a ball-and-socket joint; rotating the flexed hip inward is the motion an arthritic, inflamed joint gives up first and protests most. A hip that rotates fully and painlessly has made a significant contribution to the workup: it has argued, on examination, against the joint as the source. A hip with a short, painful internal rotation arc has done the opposite — and that finding takes sixty seconds to obtain, which is precisely why its absence from a workup is difficult to defend.
The Spine Examination Runs in Parallel
The same visit examines the other door. Straight-leg raise and crossed straight-leg raise tension the lower lumbar roots; dermatomal sensation, myotomal strength, and reflexes test whether a root is not merely irritated but malfunctioning; the pain's behavior — worse with flexion, with extension, with sitting, with walking distance — is matched against the patterns of stenosis, instability, and disc disease. A cluster of neurologic findings carries the spine side the way restricted internal rotation carries the hip side. Neither examination is a formality performed after the diagnosis is chosen. They are run together, comparatively, because the question is not "is something wrong here" — in this age group, something is wrong in both places on imaging — but "which structure is producing this pain."
Two neighboring territories are deliberately excluded from this sorting. Deep buttock pain with a normal hip examination raises the piriformis and sacroiliac questions, covered in the practice's piriformis assessment; leg pain provoked by walking distance raises the vascular question alongside the stenotic one. The hip-versus-spine sorting assumes those doors have been considered, because a two-door workup applied to a three-door problem fails the same way a one-door workup does.
Imaging Both Doors — and the Concordance Rule
Imaging follows the examination, and it images both candidates: weight-bearing radiographs of the pelvis grade the hip joint — joint-space narrowing, osteophyte formation, collapse — and lumbar imaging grades the spine. The rule that governs both is concordance. An imaging finding earns clinical weight when it agrees with the symptoms and the examination; standing alone, it earns very little, because degenerative change without symptoms is the statistical norm in this age group on both sides of the pelvis. This is the same doctrine the practice applies to lumbar MRI findings in patients whose symptoms do not match them — an image is a finding, not a verdict — and it applies to the arthritic hip on a pelvis film with exactly the same force.
The Test That Settles It: The Diagnostic Injection
When history, examination, and imaging still leave the source uncertain — the complex syndrome — the separating test is a diagnostic injection: under image guidance, local anesthetic is placed inside the hip joint, and the patient's pain is then tested against the activities that provoke it while the joint is numb. Pain that is abolished or clearly reduced during the anesthetic window identifies the joint as a source; pain that is unchanged, in a joint proven numb, redirects the workup to the spine. The test is read as evidence about contribution, not as a verdict of exclusivity — in a complex case it quantifies the hip's share, and the spine's share is assessed against what remains. It is the last step of the workup because it is the only step that tests the structure directly rather than inferring from pictures of it.
When Both Are Present: Which Is Treated First
In the both-present case, the order follows the predominant source (Devin et al., Journal of the American Academy of Orthopaedic Surgeons, 2012). The hip-dominant patient is referred for hip treatment first — and a spine surgeon who makes that referral has not failed the patient; he has done the job the patient came for. The spine-dominant patient proceeds down the spine pathway with the hip documented and followed. The secondary syndrome reverses the logic: where hip contracture is driving lumbar mechanics, treating the spine first treats the consequence. The error the entire workup exists to prevent is symmetrical and worth naming from the spine side: an operation performed correctly on the wrong structure. A technically perfect fusion, in a patient whose pain was hip-driven, produces a fused spine and the same pain — the most expensive possible way to repeat the workup.
Summary
Hip disease and spine disease are separated by method, not by the first abnormal image. Pain geography suggests, the examination discriminates — a limp, groin pain, and restricted internal rotation carrying the greatest weight (Brown et al., 2004) — and imaging of both doors is read under the concordance rule. A diagnostic hip injection settles the cases that remain complex. Both conditions present together often enough — a third of an older spine-surgery cohort carried significant hip disease on film (Lee et al., 2012) — that examining the hip is part of examining the back. The goal of the sorting is not a label. It is that the treatment, whichever door it enters, is aimed at the structure producing the pain. Patients sorting out back pain or sciatica in this practice get both examinations at the first visit, for exactly that reason.
Frequently asked questions
What is hip-spine syndrome?
It is the coexistence of hip and lumbar spine disease in which the symptoms of one mask or mimic the other, described by Offierski and MacNab in Spine in 1983. The classification distinguishes three patterns. Simple: one source is symptomatic and the other is silent. Secondary: one disease mechanically drives the other — classically, a stiff, contracted hip forcing the pelvis and lumbar spine into compensatory positions that generate back pain. Complex: both are symptomatic and no single finding establishes which predominates. The classification matters because each pattern has a different correct first move — treat the symptomatic source, treat the driver, or run the separating test before treating either.
Can hip arthritis really cause back and leg pain?
It can cause pain in the territory patients call back and leg pain, and it can cause true back pain by a mechanical route. The hip joint refers pain to the groin, the buttock, and the front of the thigh, occasionally as far as the knee — a map that overlaps the upper lumbar roots closely. Separately, an arthritic hip that loses motion develops a flexion contracture; walking with a contracted hip tilts the pelvis and holds the lumbar spine in increased lordosis, which loads the facet joints and narrows the foramina. That is the secondary syndrome: spinal pain, generated by a hip. The two mechanisms are distinguished on examination, because they are treated through different doors.
My MRI shows disc degeneration and a bulge. Doesn't that settle it?
It settles that your spine has degenerative findings, which is true of most adults past middle age, with and without pain. It does not settle that those findings produce your symptoms — that requires concordance: pain pattern, examination, and the competing sources examined and cleared. The hip is the competitor most often missed, because a lumbar MRI does not image it, and a workup that stops at the MRI never examines it. In Brown et al.'s series of leg-pain patients (Clinical Orthopaedics and Related Research, 2004), the findings that separated hip from spine sources were clinical — limp, groin pain, restricted internal rotation — not imaging findings. The MRI is one witness. It is not the jury.
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Which examination findings point to the hip?
Three carry the greatest weight in the study that measured them. Brown and colleagues (Clinical Orthopaedics and Related Research, 2004) followed 97 patients presenting with lower-extremity pain to their final diagnoses and found that patients who limped were seven times more likely to have a hip-only or combined source than a spine-only source; groin pain carried the same seven-fold association; and limited internal rotation of the hip carried a fourteen-fold association. Supporting findings include pain with the hip's rotational movements, difficulty with shoes and socks, and start-up pain on first weight-bearing after rest. No single finding is the diagnosis — the cluster is, read against the spine examination performed at the same visit.
What is a diagnostic hip injection, and what does it prove?
Under image guidance, local anesthetic is injected into the hip joint itself. The patient then performs the activities that normally provoke the pain, during the window in which the joint is numb. If the characteristic pain is abolished or clearly reduced, the joint has identified itself as a source; if the pain is unchanged in a joint proven numb, the source lies elsewhere and the workup redirects to the spine. What it proves is contribution, not exclusivity — in a patient with disease in both places, it measures the hip's share. It is used when history, examination, and imaging leave the case complex, and it is ordered before an operation is planned on either structure.
If I have both hip arthritis and spinal stenosis, which gets treated first?
The predominant source — the structure producing the greater share of the symptoms — is treated first, and the other is documented and followed (the framework set out in Devin et al., Journal of the American Academy of Orthopaedic Surgeons, 2012). Hip-dominant disease is referred for hip treatment; spine-dominant disease proceeds down the spine pathway. The exception is the secondary pattern, where a contracted hip is mechanically driving the spinal symptoms: the hip is addressed first even though the pain is felt in the back. Treating the lesser source first is the failure mode the workup exists to prevent — the treated structure heals, and the pain that brought the patient in is still there.
I had spine surgery and my leg pain is still there. Could it be my hip?
It could, and persistent pain after a technically successful operation is a classic presentation of the complex hip-spine syndrome: both sources were contributing, the spine's share was treated, and the hip's share remains. It is not the only explanation — recurrent herniation, adjacent-level disease, and incomplete decompression are assessed in parallel — but the hip belongs on the list and is examined, not assumed away. The evaluation repeats the sorting: hip examination and pelvis films if they were not done, the spine re-imaged, and a diagnostic injection if the case stays uncertain. The feared finding — that the wrong operation was done — is less common than the finding that the second source was never measured.
Does Dr. Choi treat hip arthritis?
No — Dr. Choi is a spine surgeon, and hip arthritis is treated by hip specialists. What happens in this practice is the sorting: the hip is examined at the first visit alongside the spine, pelvis imaging is reviewed when the picture requires it, and a diagnostic injection is arranged when the source remains uncertain. When the hip is the predominant source, the patient is referred to a hip colleague with the workup in hand. That referral is the system working as intended. The alternative — a spine practice that treats only what it operates on, and never examines the structure next door — is how arthritic hips end up fused around.
What should I expect at an evaluation for this?
A history that maps the pain precisely — groin, buttock, thigh, below the knee — and what provokes each part: rotation, weight-bearing, sitting, walking distance, position in bed. Then both examinations at the same visit: gait, hip range of motion with attention to internal rotation, and the neurologic examination of the legs — strength, sensation, reflexes, root-tension signs. Imaging of both doors as the findings direct: weight-bearing pelvis radiographs for the joint, lumbar imaging for the spine. And a conclusion stated in the classification's terms — spine source, hip source, hip driving spine, or complex with an injection to separate them — with the treatment order that follows from it.
Can a hip problem cause sciatica?
Not in the strict sense — sciatica (lumbar radiculopathy) is pain from an irritated or compressed lumbar nerve root, and the hip joint does not compress lumbar roots. What the hip produces is pain in overlapping territory: buttock and thigh pain that patients reasonably call sciatica because that is the word available for it. The distinction is made on examination. Radiculopathy travels below the knee in a dermatomal band and can carry neurologic signs — weakness, reflex loss, dermatomal numbness. Hip pain centers on the groin and buttock, follows the joint's movements, and restricts internal rotation. The two are confused mainly when the examination that separates them was not performed — and their treatments share almost nothing.