What physical examination maneuvers should be performed in an adult with low back pain without red‑flag features?

Physical Examination Maneuvers for Low Back Pain

Perform a focused physical examination that includes neurologic testing (motor strength, sensory examination, reflexes), straight leg raise test for radiculopathy, and assessment for red flag signs—this targeted approach allows you to classify patients into nonspecific low back pain, radiculopathy/spinal stenosis, or serious underlying pathology requiring urgent intervention. 1

Essential Components of the Physical Examination

Neurologic Assessment

• Test motor strength in key muscle groups: hip flexion (L2), knee extension (L3-L4), ankle dorsiflexion (L4-L5), great toe extension (L5), and ankle plantarflexion (S1) 1, 2
• Assess sensory function in dermatomal distributions to identify nerve root involvement 1
• Check deep tendon reflexes: patellar (L4) and Achilles (S1) reflexes to detect radiculopathy 1
• Progressive motor deficits (such as foot drop with 4/5 ankle dorsiflexion strength) constitute a red flag requiring immediate imaging 2

Straight Leg Raise Test

• Perform the straight leg raise test with the patient supine, raising the affected leg while keeping the knee extended 2
• Positive test occurs when radicular pain is reproduced at less than 60 degrees of elevation, indicating nerve root tension and radiculopathy 2
• A positive straight leg raise at 40 degrees confirms significant nerve root tension 2

Red Flag Assessment During Physical Examination

• Check for saddle anesthesia by testing sensation in the perineal region—this indicates possible cauda equina syndrome requiring emergency intervention 1, 3
• Assess anal sphincter tone if cauda equina syndrome is suspected 1
• Test for bilateral lower extremity weakness, which combined with urinary retention/incontinence suggests cauda equina syndrome 2, 3
• Palpate the spine for point tenderness that may suggest fracture, infection, or malignancy 4
• Observe gait for abnormalities that may indicate neurologic compromise or serious pathology 3

Classification Based on Physical Findings

Nonspecific Low Back Pain (>85% of cases)

• Normal neurologic examination with no radicular symptoms 1
• Negative straight leg raise test 1
• No red flag findings on history or examination 1
• These patients require no imaging and should receive conservative management immediately 1, 3

Radiculopathy or Spinal Stenosis

• Positive straight leg raise test indicating nerve root tension 2
• Dermatomal sensory deficits corresponding to specific nerve root levels 1
• Focal motor weakness in specific muscle groups 1, 2
• Diminished or absent reflexes at affected levels 1
• Imaging (MRI preferred) is only indicated after 6 weeks of failed conservative therapy in surgical candidates 1

Serious Underlying Pathology (Red Flags)

• Cauda equina syndrome signs: saddle anesthesia, bilateral leg weakness, urinary retention/incontinence, loss of anal sphincter tone 1, 3
• Progressive neurologic deficits that worsen over time 1, 2
• Fever with back pain suggesting possible spinal infection 3, 4
• Significant spinal tenderness in patients with risk factors for fracture or malignancy 4

Critical Pitfalls to Avoid

• Do not skip the neurologic examination—motor, sensory, and reflex testing is essential to identify radiculopathy and serious pathology 1
• Do not order imaging based on physical findings alone in the absence of red flags or after less than 6 weeks of conservative therapy 1
• Do not assume imaging abnormalities correlate with symptoms—disc protrusions are present in 29-43% of asymptomatic individuals 2, 5
• Do not delay urgent evaluation when red flags are present, particularly cauda equina syndrome which requires emergency imaging and intervention 1, 3
• Do not perform extensive diagnostic testing in patients with nonspecific low back pain and normal neurologic examination, as this provides no clinical benefit 1

Additional Examination Considerations

• Assess for spinal deformity including scoliosis or kyphosis, particularly in pediatric patients where this may indicate serious pathology 3
• Evaluate range of motion in the lumbar spine, though this has limited diagnostic value for specific pathology 6
• Palpate for paraspinal muscle spasm, which is common but nonspecific 6, 7
• Screen for psychosocial risk factors (yellow flags) during the examination that predict risk for chronic disabling back pain, including fear-avoidance behaviors and catastrophizing 1, 8