What are the common and serious differential diagnoses for lumbar pain and how should it be initially managed when no red‑flag features are present?

Differential Diagnosis and Initial Management of Lumbar Pain Without Red Flags

For adults with acute lumbar pain and no red-flag symptoms, imaging is not indicated; instead, initiate immediate conservative management consisting of patient education to remain active, oral NSAIDs or acetaminophen for pain control, and reassurance about the favorable natural history—most cases resolve spontaneously within 4–6 weeks. 1, 2, 3

Common Differential Diagnoses

Nonspecific Mechanical Low Back Pain (≈85% of cases)

• Musculoskeletal strain or sprain: The vast majority of lumbar pain stems from muscle, ligament, or facet joint injury without identifiable structural pathology. 4, 5
• Degenerative disc disease: Age-related disc changes are extremely common in asymptomatic individuals (disc protrusions present in up to 43% of asymptomatic 80-year-olds) and often do not correlate with symptoms. 3, 6
• Facet joint arthropathy: Degenerative changes in the facet joints can produce axial back pain without radicular features. 7

Lumbar Radiculopathy (≈10–15% of cases)

• Herniated nucleus pulposus: Disc herniation causing nerve root compression presents with dermatomal pain, sensory deficits, focal motor weakness, and positive straight-leg-raise test. 2, 6
• Spinal stenosis: Narrowing of the spinal canal or neural foramina produces neurogenic claudication—pain with walking that improves with sitting or forward flexion. 7, 5

Serious Pathology Requiring Red-Flag Screening (<5% of cases)

• Cauda equina syndrome: Urinary retention/incontinence, saddle anesthesia, bilateral leg weakness, and loss of anal sphincter tone mandate emergent MRI and surgical referral. 2, 3, 4
• Malignancy: History of cancer, unexplained weight loss, age >50 with new-onset pain, or night pain unrelieved by rest. 1, 3, 8
• Infection (discitis/osteomyelitis/epidural abscess): Fever, IV drug use, immunosuppression (diabetes, HIV, dialysis), or recent spinal procedure. 1, 3, 8
• Fracture: Significant trauma, osteoporosis, prolonged corticosteroid use, or age >70. 3, 9, 8
• Inflammatory spondyloarthropathy: Morning stiffness >30 minutes, improvement with activity, age <40 at onset. 7, 9

Initial Management Algorithm (No Red Flags Present)

Step 1: Red-Flag Screening

Screen every patient for the following red flags; their presence mandates urgent imaging and specialist referral: 2, 3, 8

• Cauda equina syndrome symptoms (urinary retention, saddle anesthesia, bilateral leg weakness)
• Progressive motor deficits (e.g., new foot drop)
• Suspected malignancy (history of cancer, unexplained weight loss, age >50 with new pain)
• Suspected infection (fever, IV drug use, immunosuppression)
• Fracture risk (significant trauma, osteoporosis, prolonged steroid use)

Step 2: Physical Examination

Perform a focused neurologic examination to classify the pain pattern: 6

• Motor strength testing: Hip flexion (L2), knee extension (L3–L4), ankle dorsiflexion (L4–L5), great-toe extension (L5), ankle plantarflexion (S1)
• Sensory assessment: Dermatomal distribution to detect nerve-root involvement
• Reflex testing: Patellar (L4) and Achilles (S1) reflexes
• Straight-leg-raise test: Positive if radicular pain reproduced at <60 degrees of leg elevation
• Saddle anesthesia check: Perineal sensory loss indicates possible cauda equina syndrome

Step 3: Avoid Routine Imaging

Do not order imaging (X-ray, MRI, CT) during the initial evaluation of uncomplicated lumbar pain without red flags—it provides no clinical benefit and increases unnecessary healthcare utilization. 1, 2, 3

The ACR Appropriateness Criteria explicitly state that routine imaging in acute (<4 weeks) or subacute/chronic uncomplicated low back pain is not useful because: 1

• Most cases are self-limiting and responsive to conservative management
• Imaging abnormalities are common in asymptomatic individuals and do not correlate with symptoms
• Early imaging (<6 weeks) is associated with higher rates of unnecessary injections, surgical interventions, and disability claims without improved outcomes 3
• The majority of disc herniations undergo spontaneous reabsorption by approximately 8 weeks after symptom onset 2, 6

Step 4: First-Line Conservative Management

Pharmacologic Therapy

• Oral NSAIDs (first-line): Ibuprofen 400–800 mg three times daily, naproxen 500 mg twice daily, or diclofenac 50 mg twice daily provide moderate short-term pain relief. 2, 3
• Acetaminophen (alternative): May be used if NSAIDs are contraindicated, though evidence shows limited benefit over placebo. 2, 3
• Skeletal muscle relaxants (adjunct): Can be added for short-term relief when NSAIDs/acetaminophen are insufficient; use with caution due to sedation. 2
• Avoid systemic corticosteroids: Trials show no superiority over placebo for sciatica. 2
• Avoid gabapentin/antiepileptics: Insufficient evidence for radicular low back pain. 2

Monitor all NSAID use for gastrointestinal, cardiovascular, and renal adverse effects, especially in older patients or those with prolonged use. 2

Non-Pharmacologic Therapy

• Activity advice (critical): Encourage patients to remain active and continue ordinary activities within pain limits; bed rest should be avoided because it delays recovery. 2, 3, 5
• Spinal manipulation: The only non-pharmacologic intervention with proven short-term benefit for acute low back pain (<4 weeks), providing small-to-moderate improvements in pain and function. 2
• Avoid supervised exercise programs initially: Not effective for acute low back pain; consider beginning structured exercise 2–6 weeks after symptom onset if symptoms persist. 2

Step 5: Reassessment and Escalation (After 6 Weeks)

Reassess pain and functional status within 2–4 weeks of initiating therapy; if symptoms persist beyond 6 weeks despite optimal conservative management, consider MRI lumbar spine without contrast only for patients who are potential surgical candidates or candidates for epidural steroid injection. 2, 3, 6

Criteria for delayed imaging after 6 weeks: 3, 6

• Inadequate response to conservative therapy
• Patient is being evaluated for possible surgical or interventional treatment
• Persistent radicular symptoms with documented functional limitation

Interventional options after failed conservative therapy: 6

• Epidural steroid injections for radiculopathy specifically (fluoroscopic guidance is the gold standard)
• Radiofrequency ablation for chronic pain with suspected facet involvement (after positive medial branch blocks)
• Surgical referral for persistent radicular symptoms with documented nerve root compression on MRI

Critical Pitfalls to Avoid

• Never order imaging before 6 weeks unless red flags are present—this leads to detection of incidental findings in asymptomatic individuals, triggering unnecessary interventions and worsening outcomes. 1, 3, 6
• Never prescribe complete bed rest—remaining active is more effective than bed rest and prevents prolonged disability. 2, 3, 5
• Never assume imaging abnormalities correlate with symptoms—degenerative changes increase with age and are often asymptomatic. 3, 6
• Never delay urgent evaluation when red-flag signs are present—cauda equina syndrome and progressive motor deficits require emergency imaging and intervention to prevent permanent neurologic injury. 2, 3, 8
• Never omit the neurologic examination—motor, sensory, and reflex testing are essential for detecting radiculopathy and serious conditions. 6

Special Considerations for Pediatric Patients

For children with back pain, radiographs may be useful as initial imaging if red flags are present (diagnostic yield up to 24% when combined with detailed history and physical examination). 3

Pediatric red flags include: 1, 3

• Morning stiffness, gait abnormalities, night pain
• Neurologic deficit, radiating pain
• Fever, weight loss, pain >4 weeks
• Abnormal spinal curvature

MRI without contrast is the preferred advanced imaging if red flags are present or conservative treatment fails in children. 1, 3