What are the recommended steps for diagnosing and managing low back pain?

Diagnosing Low Back Pain: A Structured Clinical Approach

Begin with a focused history and physical examination to categorize patients into one of three groups: nonspecific low back pain (85% of cases), back pain with radiculopathy or spinal stenosis, or back pain with a specific serious spinal cause—this classification drives all subsequent diagnostic and management decisions. 1, 2

Initial History: Critical Elements to Assess

Pain Characteristics

• Location and radiation pattern: Determine if pain is localized to the back versus radiating into the legs following a dermatomal distribution (suggesting radiculopathy) 2, 3
• Temporal pattern: Ask about frequency (constant versus intermittent), duration, and whether symptoms worsen with specific activities like walking (suggesting spinal stenosis) 2
• Previous episodes: Document prior treatments attempted and their effectiveness 2

Red Flags Requiring Urgent Evaluation

Screen systematically for serious underlying conditions that demand immediate imaging and workup 1, 2, 3:

• Malignancy indicators: History of cancer (increases probability to 9%, positive likelihood ratio 14.7), unexplained weight loss (positive likelihood ratio 2.7), age >50 years (positive likelihood ratio 2.7), or failure to improve after 1 month (positive likelihood ratio 3.0) 2, 3
• Infection risk: Fever, recent infection, intravenous drug use, or immunocompromised status 3
• Neurological emergency: Rapidly progressive or severe neurologic deficits, bladder or bowel dysfunction (cauda equina syndrome—a surgical emergency occurring in 0.04% of cases) 2, 3
• Trauma: Significant recent trauma suggesting possible fracture 1, 2

Neurological Symptoms

• Radicular pain (sciatica): Leg pain radiating below the knee in a dermatomal pattern, present in symptomatic herniated disc (4% of cases) 3
• Pseudoclaudication: Leg pain and weakness with walking or standing that improves with sitting or spinal flexion, characteristic of spinal stenosis (3% of cases) 3
• Motor weakness: Document specific muscle groups affected 2

Psychosocial Risk Factors ("Yellow Flags")

Assessment of psychological factors is mandatory as they predict risk for chronic disabling back pain more reliably than anatomical findings 1, 2, 3. Screen for depression, anxiety, catastrophizing, fear-avoidance behaviors, and job dissatisfaction.

Non-Spinal Sources

Consider referred pain from pancreatitis, nephrolithiasis, aortic aneurysm, endocarditis, or other systemic illnesses 2

Physical Examination: Targeted Maneuvers

Perform neurological testing including motor strength, sensory examination, and reflex testing to identify nerve root involvement 2. Assess for palpable muscle spasm and range of motion limitations 2. Conduct straight leg raise testing for radiculopathy and specific provocative tests for spinal stenosis.

Diagnostic Imaging: When and What to Order

For Nonspecific Low Back Pain (No Red Flags)

Do NOT routinely obtain imaging or other diagnostic tests—this is a strong recommendation based on moderate-quality evidence 1. Routine imaging in this population leads to unnecessary procedures, increased costs, and does not improve outcomes 3.

For Red Flags or Serious Pathology

Perform diagnostic imaging immediately when severe or progressive neurologic deficits are present or when serious underlying conditions are suspected 1. Order MRI without and with contrast, along with laboratory studies including complete blood count, erythrocyte sedimentation rate, and C-reactive protein 3.

For Persistent Radiculopathy or Spinal Stenosis

Obtain MRI (preferred) or CT only if the patient is a potential candidate for surgery or epidural steroid injection 1, 2. This prevents imaging findings from driving treatment in patients who would not benefit from interventional approaches.

Initial Management Based on Diagnostic Category

For Nonspecific Low Back Pain

• Provide reassurance and evidence-based education about the expected favorable course—90% of acute cases resolve within one month 1
• Advise patients to remain active and provide information about effective self-care options 1
• Consider first-line medications: Acetaminophen or nonsteroidal anti-inflammatory drugs, assessing baseline pain severity, functional deficits, and potential risks before initiating therapy 1

For Radiculopathy or Spinal Stenosis

Proceed with MRI if surgical or interventional candidacy exists, then consider epidural steroid injections for radiculopathy (though evidence is mixed) 1

For Specific Serious Spinal Causes

Urgent referral and treatment based on the underlying condition (malignancy 0.7%, compression fracture 4%, spinal infection 0.01%, ankylosing spondylitis 0.3-5%) 2, 3

Critical Pitfalls to Avoid

• Delaying imaging when red flags are present can result in permanent disability, particularly with cauda equina syndrome 3
• Over-imaging patients with nonspecific low back pain wastes resources and leads to identification of incidental findings that drive unnecessary interventions 3
• Attributing pain to imaging findings without clinical correlation causes misdiagnosis—many asymptomatic individuals have disc bulges and degenerative changes on imaging 3
• Ignoring psychosocial factors means missing the strongest predictors of chronicity and disability 3