Residency · Residency · Physical Medicine Rehabilitation

Low Back Pain: A Physiatric Approach

Epidemiology and Burden

Low back pain (LBP) is the leading cause of disability worldwide (Global Burden of Disease studies). Lifetime prevalence of 60-80% in the general population. 90% of acute LBP episodes resolve within 6-12 weeks regardless of treatment. 5-10% develop chronic LBP (>12 weeks), consuming the vast majority of healthcare resources. LBP is the most common reason for physiatric consultation.

Classification of Low Back Pain

By Duration

Acute: <4 weeks. Subacute: 4-12 weeks (critical window for prevention of chronicity). Chronic: >12 weeks.

By Mechanism/Source

Mechanical/Non-specific (~85%): no identifiable specific structural cause. Discogenic: internal disc disruption, disc herniation. Facetogenic: facet (zygapophyseal) joint arthropathy. Sacroiliac joint: SI joint dysfunction or arthropathy.

Myofascial: paraspinal muscle strain, trigger points. Spinal stenosis: central or lateral recess stenosis (neurogenic claudication). Radiculopathy: nerve root compression with dermatomal symptoms. Serious pathology (<1%): fracture, malignancy, infection, cauda equina syndrome.

Red Flags (Require Urgent Workup)

Cauda equina syndrome: saddle anesthesia, urinary retention, bilateral leg weakness. Progressive neurological deficit. History of malignancy with new back pain. Unexplained weight loss, fevers, night sweats.

Recent significant trauma (or minor trauma in osteoporotic patient). IV drug use or immunosuppression (infection risk). Age >50 or <18 with new onset back pain. Pain that is worse at night, unrelenting, not relieved by position change.

Yellow Flags (Psychosocial Risk Factors for Chronicity)

Fear-avoidance beliefs about activity and work. Catastrophizing and pain catastrophization. Depression and anxiety. Passive coping strategies. Job dissatisfaction, secondary gain, pending litigation. Low self-efficacy for pain management. Social isolation.

The Biopsychosocial Model

LBP management must address biological, psychological, and social contributors simultaneously. Purely biomedical approaches (imaging, injections, surgery) for non-specific LBP have limited long-term efficacy. Early identification and management of yellow flags is critical to prevent transition to chronicity. Patient education about the benign nature of most LBP is therapeutic in itself. Active self-management approaches consistently outperform passive treatments.

Clinical Evaluation

History

Onset, duration, location, radiation pattern. Aggravating and relieving factors (mechanical vs. inflammatory vs. constant). Neurological symptoms: radicular pain, numbness, weakness, bowel/bladder changes. Functional impact: ADLs, work, sleep, psychosocial function. Prior treatments and response. Psychosocial screening (STarT Back tool, Orebro Musculoskeletal Pain Questionnaire).

Physical Examination

Observation: posture, antalgic gait, spinal alignment, muscle guarding. Range of motion: flexion, extension, lateral flexion, rotation. Palpation: spinous processes, paraspinal muscles, SI joints. Neurological examination: myotomes (L2-S1), dermatomes, reflexes (patellar L4, Achilles S1).

Straight leg raise (SLR): sensitivity ~91% for L4-S1 disc herniation; crossed SLR specificity ~88%. Femoral nerve stretch test: for upper lumbar (L2-L4) radiculopathy. Special tests: FABER/Patrick test (SI joint/hip), Waddell signs (non-organic pain behavior). Hip examination: always assess for hip OA as a mimicker of LBP.

Imaging

When NOT to Image

Acute non-specific LBP without red flags (first 4-6 weeks). ACP/APS guidelines recommend against routine imaging for non-specific LBP. Incidental findings (disc bulges, degenerative changes) are highly prevalent in asymptomatic individuals and can lead to unnecessary intervention.

When to Image

Red flags present. Progressive neurological deficit. Failure to improve after 4-6 weeks of conservative management. Suspected radiculopathy being considered for interventional treatment.

MRI: preferred for soft tissue evaluation (disc herniation, neural compression, infection, tumor). CT: better for bony detail (fracture, spondylolysis). Radiographs: scoliosis screening, alignment, fracture, spondylolisthesis.

Evidence-Based Management

First-Line (Non-Pharmacologic)

Patient education: reassurance, expected timeline, activity advice. Staying active: avoid bed rest (evidence of harm with prolonged rest). Physical therapy: exercise-based approach is the cornerstone. Motor control exercises (core stabilization).

McKenzie method (directional preference). General strengthening and aerobic conditioning. Yoga, Pilates, tai chi (moderate evidence). Cognitive behavioral therapy (CBT): strong evidence for chronic LBP, addresses fear-avoidance.

Multidisciplinary rehabilitation: combined physical and psychological approaches for chronic LBP (strongest evidence for functional improvement). Spinal manipulation: short-term benefit in acute LBP.

Pharmacologic Management

Acetaminophen: limited evidence of efficacy for LBP (PACE trial showed no benefit over placebo for acute LBP). NSAIDs: first-line pharmacologic option for acute LBP; short course (2-4 weeks), consider GI and renal risks. Muscle relaxants: short-term use (<2 weeks) for acute spasm (cyclobenzaprine, tizanidine). Duloxetine: FDA-approved for chronic musculoskeletal pain including LBP; NNT ~7.

Tramadol: weak opioid option for moderate pain, preferred over strong opioids. Opioids: last resort, short course only, avoid in chronic non-specific LBP (evidence of harm with long-term use). Gabapentinoids: may be considered for radicular pain, but evidence for non-specific LBP is weak. Topical agents: lidocaine patches, topical NSAIDs (limited evidence for axial LBP).

Interventional Options

Epidural steroid injection (ESI): short-term relief for radiculopathy (4-6 weeks); interlaminar, transforaminal, or caudal approaches. Facet joint interventions: medial branch blocks (diagnostic) followed by radiofrequency ablation if positive (50-80% pain relief for 6-12 months). SI joint injection: diagnostic and therapeutic; consider radiofrequency ablation for confirmed SI joint pain. Trigger point injections: for myofascial component. Regenerative therapies: PRP, prolotherapy (emerging evidence, not yet standard of care).

Surgical Referral

Cauda equina syndrome (emergency). Progressive neurological deficit despite conservative care. Refractory radiculopathy with concordant imaging after 6-12 weeks of conservative treatment. Spinal stenosis with significant neurogenic claudication limiting function.

Spondylolisthesis with instability and failed conservative care. Surgery for non-specific axial LBP (fusion) has limited evidence and should be a last resort.

Physical Therapy Prescription for the Physiatrist

Prescriptions should be specific: diagnosis, precautions, frequency, goals. Specify treatment approach when appropriate (e.g., McKenzie, motor control, aquatic therapy). Typical frequency: 2-3 times per week for 6-8 weeks, then transition to home program. Emphasize active over passive modalities. Functional goals: return to work, ADL independence, exercise tolerance.

<image>Sagittal cross-section of the lumbar spine showing the intervertebral disc (annulus fibrosus and nucleus pulposus), vertebral body, facet joint, spinal canal with cauda equina nerve roots, and neural foramen. Demonstrate a posterolateral disc herniation compressing the traversing nerve root. Label the posterior longitudinal ligament, ligamentum flavum, and epidural space.</image>

<image>Flowchart diagram showing the evidence-based approach to low back pain evaluation: starting with history and red flag screening, branching into emergency workup (if red flags present) versus conservative management (if no red flags). The conservative pathway shows first-line treatments (education, activity, PT, NSAIDs), reassessment at 4-6 weeks, and escalation to imaging and interventional options if symptoms persist. Include yellow flag screening at the subacute phase branching to multidisciplinary rehabilitation.</image>

<image>Posterior view of the lumbar spine and pelvis showing the dermatome map for L1 through S1 nerve roots on the lower extremity, with myotome testing positions illustrated alongside: L2 hip flexion, L3 knee extension, L4 ankle dorsiflexion, L5 great toe extension, S1 ankle plantarflexion. Include reflex arc locations for patellar (L4) and Achilles (S1) reflexes.</image>

Clinical Pearls

The single most important intervention in acute LBP is reassurance and advice to stay active -- avoid prescribing bed rest. Always screen for cauda equina syndrome: ask about bladder function and saddle numbness at every visit. The STarT Back Screening Tool efficiently stratifies patients into low, medium, and high risk for chronicity and guides treatment intensity. Imaging findings correlate poorly with symptoms: 30-40% of asymptomatic individuals have disc herniations on MRI.

Early psychosocial intervention (within 4-6 weeks) for patients with yellow flags is more effective than waiting until pain becomes chronic. Avoid the term "degenerative disc disease" with patients -- it can increase fear and catastrophizing; use "normal age-related changes". Facet joint pain is suggested by extension-loading pain but cannot be reliably diagnosed by examination alone; diagnostic medial branch blocks are required. Chronic LBP is best managed with a multidisciplinary approach combining exercise, CBT, and self-management -- no single modality is sufficient.

References

• Maher C, Underwood M, Buchbinder R. Non-specific low back pain. Lancet. 2017;389(10070):736-747.
• Qaseem A, et al. Noninvasive treatments for acute, subacute, and chronic low back pain: a clinical practice guideline from the ACP. Ann Intern Med. 2017;166(7):514-530.
• Foster NE, et al. Prevention and treatment of low back pain: evidence, challenges, and promising directions. Lancet. 2018;391(10137):2368-2383.
• Williams CM, et al. Efficacy of paracetamol for acute low-back pain: a double-blind, randomised controlled trial (PACE). Lancet. 2014;384(9954):1586-1596.
• Hill JC, et al. Comparison of stratified primary care management for low back pain with current best practice (STarT Back). Lancet. 2011;378(9802):1560-1571.
• Brinjikji W, et al. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR Am J Neuroradiol. 2015;36(4):811-816.

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