What is the systematic approach to performing a back physical examination?

Systematic Approach to Back Physical Examination

A thorough back physical examination should include neurological testing (motor, sensory, reflexes), palpation of spinous processes, assessment of spinal curvature, gait testing, range of motion evaluation, and inspection for skin abnormalities, with the primary goal of categorizing patients into nonspecific mechanical pain, radiculopathy/spinal stenosis, or serious underlying pathology to guide imaging decisions and management. 1, 2

Essential Components of the Physical Examination

Inspection and Observation

• Observe gait pattern to identify antalgic gait, foot drop, or abnormal walking mechanics that suggest nerve root involvement 1
• Inspect the skin for café-au-lait spots, hairy patches, dimples, or other cutaneous markers of underlying spinal dysraphism 1
• Assess spinal curvature for scoliosis, kyphosis, or loss of normal lordosis 1
• Look for visible muscle asymmetry or atrophy suggesting chronic denervation 3

Palpation

• Palpate each spinous process systematically from cervical through lumbar spine to identify point tenderness suggesting fracture, infection, or inflammatory disease 1
• Assess paraspinal muscles for spasm, trigger points, or asymmetric tension 1
• Palpate the sacroiliac joints for tenderness suggesting sacroiliitis 4

Range of Motion Testing

• Test flexion, extension, lateral bending, and rotation of the spine, noting which movements reproduce or worsen pain 1
• Mechanical pain pattern (worsening with activity, improving with rest) suggests nonspecific mechanical low back pain 4
• Inflammatory pain pattern (morning stiffness >30 minutes improving with movement) suggests spondyloarthritis 4

Neurological Examination

Motor Testing

• L4 nerve root: Test ankle dorsiflexion strength 2
• L5 nerve root: Test great toe extension (extensor hallucis longus) 2, 3
• S1 nerve root: Test ankle plantarflexion and toe walking 2, 3
• Document motor weakness using a standardized grading scale, as progressive motor deficits warrant immediate imaging 2, 5

Sensory Testing

• Perform dermatomal sensory testing to map the exact distribution of numbness or paresthesias to specific nerve roots 2
• Distinguish dermatomal from non-dermatomal patterns, as the former suggests radiculopathy while the latter suggests nonspecific pain 2
• Test light touch, pinprick, and proprioception systematically 6, 3

Reflex Testing

• Patellar reflex (L4): Assess for diminished or absent response 2
• Achilles reflex (S1): Assess for diminished or absent response 2, 3
• Asymmetric or absent reflexes support radiculopathy diagnosis 3

Provocative Testing

• Straight leg raise test: Perform with patient supine, raising the affected leg while keeping knee extended; positive if radicular pain reproduced at <70 degrees (odds ratio 3.0 for nerve root compression) 3
• Crossed straight leg raise: Pain in the affected leg when raising the contralateral leg is highly specific for disc herniation 3
• Assess for pain with coughing, sneezing, or straining (Valsalva maneuver), which increases intraspinal pressure and suggests nerve root compression (odds ratio 2.4) 3

Critical Red Flag Assessment

Immediate Imaging Indicators

• Urinary retention or new-onset fecal incontinence suggests cauda equina syndrome requiring urgent MRI 2, 7, 5
• Saddle anesthesia (perineal numbness) indicates cauda equina syndrome 4, 7
• Multiple-level motor deficits suggest cauda equina or extensive cord compression 2, 7
• Fever with back pain raises concern for spinal infection (prevalence 0.01%) 7, 5

High-Risk Historical Features

• History of cancer has the strongest predictive value for malignancy (positive likelihood ratio 14.7, increasing post-test probability from 0.7% to 9%) 4, 8
• Age >50 years increases fracture risk (post-test probability 9%) 8
• Prolonged corticosteroid use substantially increases fracture risk (post-test probability 33%) 8
• Severe trauma or presence of contusion/abrasion increases fracture probability (11% and 62% respectively) 8
• Unexplained weight loss suggests malignancy 7

Common Pitfalls to Avoid

• Do not routinely order imaging for nonspecific back pain without red flags, as this does not improve outcomes and leads to unnecessary interventions and radiation exposure 1, 4, 5
• Do not overlook inflammatory causes in younger patients (<45 years) with chronic symptoms and morning stiffness >30 minutes, as early diagnosis of spondyloarthritis allows for disease-modifying treatment 4
• Do not dismiss psychosocial factors: Depression, anxiety, passive coping strategies, and job dissatisfaction are stronger predictors of chronicity than physical examination findings 2
• Do not assume normal examination excludes serious pathology in high-risk patients (elderly, cancer history, immunosuppressed), as these patients warrant lower threshold for imaging 2, 7
• Multiple red flags together dramatically increase fracture probability to 90%, warranting immediate imaging 8

Documentation and Follow-Up Strategy

• Categorize findings into one of three groups: nonspecific mechanical pain (>85% of cases), radiculopathy/spinal stenosis (~7% of cases), or serious underlying pathology (<1% of cases) 2, 4
• Reevaluate within 1 month if symptoms persist or worsen, with earlier reassessment for severe symptoms, progressive deficits, or new red flags 2
• Lower threshold for imaging in elderly patients (>65-70 years) due to higher prevalence of serious pathology 2