What are the recommended steps for managing sudden onset low back pain radiating down to the left ankle without a known injury?

Management of Acute Low Back Pain with Radiculopathy

For sudden low back pain radiating to the ankle without known injury, do NOT obtain imaging initially—instead, provide reassurance about the favorable natural history, advise remaining active, prescribe NSAIDs or acetaminophen for pain control, and perform a focused neurological examination to assess for red flags. 1, 2

Initial Clinical Assessment

Perform a targeted neurological examination focusing on:

• Straight leg raise test between 30-70 degrees (91% sensitivity for herniated disc, though only 26% specificity) 1
• Motor strength testing of ankle dorsiflexion (L5 nerve root) and foot plantarflexion (S1 nerve root) 1
• Ankle reflexes (S1 nerve root) and sensory distribution along the leg 1
• Red flag screening for cauda equina syndrome (new urinary retention/incontinence, saddle anesthesia, progressive motor weakness), malignancy, infection, or fracture 1, 2

Critical pitfall: The crossed straight-leg-raise test is more specific (88%) but less sensitive (29%) than the standard straight-leg raise, so use both tests together for better diagnostic accuracy 1

Imaging Decisions

Do NOT order imaging for this presentation unless red flags are present 1, 2, 3. The evidence is clear:

• Acute uncomplicated low back pain with radiculopathy (<4 weeks duration) is self-limiting in most patients and improves within the first month regardless of imaging 1
• Routine imaging provides no clinical benefit and exposes patients to unnecessary radiation 1, 3
• Disc abnormalities are found in 29% of asymptomatic 20-year-olds and 43% of asymptomatic 80-year-olds, making findings poorly correlated with symptoms 1, 3
• Most disc herniations show reabsorption by 8 weeks after symptom onset 1, 3

When imaging IS indicated:

• Immediate MRI (preferred over CT) if red flags present: cauda equina syndrome, progressive neurologic deficits, or suspected malignancy/infection 1, 2, 4
• MRI after 4-6 weeks of conservative management if symptoms persist without improvement AND the patient is a surgical candidate or candidate for epidural steroid injection 1, 4

Initial Management Strategy

Non-Pharmacologic (First-Line)

Advise the patient to remain active rather than bed rest—this is more effective for reducing disability 1, 2. Provide:

• Superficial heat application using heating pads for short-term relief 1, 2
• Self-care education with evidence-based materials like "The Back Book" 1
• Reassurance about the favorable prognosis—most patients experience substantial improvement within the first month 1, 2

For acute/subacute pain, consider adding:

• Spinal manipulation (small to moderate short-term benefits) 1, 2
• Massage therapy 1, 2
• Acupuncture 1, 2

Pharmacologic (Second-Line, If Needed)

First choice: NSAIDs (moderate-quality evidence for effectiveness) 1, 2

Alternative: Acetaminophen up to 4g daily for mild-to-moderate pain 2

If inadequate response: Skeletal muscle relaxants for short-term use (moderate-quality evidence) 1, 2

Avoid:

• Systemic corticosteroids (not more effective than placebo) 1, 2
• Opioids for initial management (abuse potential without superior efficacy) 2
• Benzodiazepines (risks for abuse, addiction, tolerance) 1

Follow-Up and Reassessment

Reevaluate at 4-6 weeks if symptoms persist without improvement 1, 2, 3. Earlier reassessment is warranted for:

• Severe pain or functional deficits 1
• Older patients 1
• Worsening neurologic symptoms 2

At the 4-6 week reassessment, if no improvement:

• Consider MRI (preferred) or CT to evaluate for disc herniation or nerve root compression 1, 4
• Refer for physical therapy or intensive rehabilitation 2
• Assess psychosocial risk factors using tools like STarT Back, as these predict progression to chronic pain better than physical findings 1, 2

Psychosocial Risk Assessment

Screen for factors predicting poor outcomes 1, 2:

• Depression or anxiety
• Passive coping strategies
• Job dissatisfaction
• Fear-avoidance beliefs
• Disputed compensation claims

These psychosocial factors are stronger predictors of outcomes than physical examination findings or pain severity 1

Common Pitfalls to Avoid

• Ordering routine imaging in the first 4-6 weeks without red flags—this increases healthcare costs without improving outcomes and may lead to unnecessary interventions 1, 3
• Prescribing bed rest—activity maintenance is superior for recovery 1, 2
• Starting opioids as initial therapy—reserve as last resort with careful monitoring 2
• Failing to reassess patients with persistent symptoms after 1 month 1, 2