What assessment should be performed on a patient presenting with low back pain?

Assessment of Low Back Pain

Perform a focused history and physical examination to categorize the patient into one of three groups: nonspecific low back pain (>85% of cases), back pain with radiculopathy or spinal stenosis (~7%), or back pain with specific underlying pathology (<2%), while simultaneously screening for red flags and psychosocial risk factors. 1, 2

History Components

Red Flag Screening (Immediate Identification Required)

Screen systematically for conditions requiring urgent intervention:

• Cauda equina syndrome (0.04% prevalence): Ask about urinary retention, fecal incontinence, saddle anesthesia, and bilateral leg weakness 2
• Malignancy (0.7% prevalence): Inquire about history of cancer (increases probability from 0.7% to 9%), unexplained weight loss, age >50, and failure to improve with therapy 2
• Vertebral compression fracture (4% prevalence): Document history of osteoporosis, steroid use, or significant trauma 2
• Spinal infection (0.01% prevalence): Ask about fever, recent infection, IV drug use, or immunocompromised status 2
• Progressive neurologic deficits: Document any worsening motor or sensory loss 1, 3

Pain Pattern Characterization

Distinguish between mechanical and inflammatory patterns:

• Mechanical pattern (suggests nonspecific low back pain): Pain worsens with activity and improves with rest 4
• Inflammatory pattern (suggests spondyloarthritis, 0.3-5% prevalence in chronic cases): Morning stiffness >30 minutes that improves with movement and worsens with rest, particularly in patients <45 years 2, 4
• Radicular pattern (suggests herniated disc, 4% prevalence): Sciatica with dermatomal distribution, leg pain worse than back pain 2
• Pseudoclaudication (suggests spinal stenosis, 3% prevalence): Bilateral leg symptoms, older age, symptoms worse with standing/walking and relieved by sitting or forward flexion 2

Psychosocial Risk Factor Assessment ("Yellow Flags")

Evaluate factors predicting chronic disability and poor outcomes:

• Depression and anxiety 1, 2
• Passive coping strategies and catastrophizing 1, 2
• Job dissatisfaction 1, 2
• Fear-avoidance beliefs 2
• Higher baseline disability levels 1

Use the STarT Back tool at 2 weeks to risk-stratify patients for appropriate resource allocation. 2, 3

Physical Examination Components

Neurologic Examination

• Straight leg raise test: Perform to evaluate for radiculopathy (positive if reproduces leg pain at <60 degrees) 2, 3
• Motor strength testing: Assess specific nerve root distributions (L4: ankle dorsiflexion, L5: great toe extension, S1: ankle plantarflexion) 2
• Sensory examination: Test dermatomal patterns for sensory deficits 2
• Reflexes: Check patellar (L4) and Achilles (S1) reflexes 2
• Saddle anesthesia testing: Essential if cauda equina syndrome suspected 2

Spinal Examination

• Midline tenderness: Palpate for point tenderness suggesting vertebral compression fracture (especially with osteoporosis/steroid use) or infection (if accompanied by fever) 3
• Paraspinal muscle spasm: Document presence, which may accompany radiculopathy 2
• Range of motion: Assess lumbar flexion, extension, and lateral bending 5

Imaging Strategy

Do NOT Order Routine Imaging

Avoid imaging in nonspecific low back pain without red flags, as this does not improve outcomes and exposes patients to unnecessary radiation (equivalent to daily chest x-rays for >1 year in gonadal radiation). 1, 2, 3

When to Order Imaging Immediately

• Immediate MRI or CT (MRI preferred for better soft tissue visualization and no radiation): 1, 2, 3
  • Suspected cauda equina syndrome
  • Severe or progressive neurologic deficits
  • Suspected malignancy, infection, or fracture based on red flags

When to Order Delayed Imaging

• Plain radiography at 4-6 weeks: Consider only if symptoms persist despite conservative management and patient has risk factors for compression fracture 3
• MRI at 4-6 weeks: For persistent radiculopathy or spinal stenosis symptoms in patients who are potential candidates for surgery or epidural steroid injection 1, 3

Functional Assessment

Document baseline disability using the Roland-Morris Disability Questionnaire (RDQ, 0-24 scale), where a 2-5 point improvement represents clinically significant change. 3

Critical Pitfalls to Avoid

• Missing cauda equina syndrome leads to permanent neurologic disability from delayed surgical decompression 2
• Overlooking cancer in patients with prior malignancy, where posttest probability jumps from 0.7% to 9% 2
• Failing to recognize inflammatory causes in younger patients (<45 years) with chronic symptoms and morning stiffness delays access to highly effective TNF-blocking agents 2
• Ordering routine imaging for uncomplicated acute low back pain exposes patients to unnecessary radiation without clinical benefit 1, 2, 3