Musculoskeletal Assessment for Back Pain
Initial Diagnostic Triage
Conduct a focused history and physical examination to classify patients into one of three categories: nonspecific low back pain (85% of cases), back pain with radiculopathy or spinal stenosis, or back pain with another specific spinal cause requiring urgent evaluation. 1
Critical History Elements
- Duration and pattern: Document onset, frequency, and any prior episodes with treatment responses 1
- Pain location and radiation: Assess for sciatica (leg pain worse than back pain) suggesting radiculopathy or pseudoclaudication suggesting spinal stenosis 1
- Red flag screening for serious pathology 1:
- History of cancer (increases probability from 0.7% to 9%)
- Unexplained weight loss
- Age >50 years
- Fever or recent infection (spinal infection prevalence 0.01%)
- Failure to improve after 1 month
- IV drug use
- Immunosuppression
Essential Physical Examination Components
Neurologic assessment 1:
- Motor strength testing at multiple levels (L2-S1)
- Sensory examination in dermatomal distribution
- Reflexes (patellar, Achilles)
- Straight leg raise test (positive if reproduces leg pain at <60 degrees)
Cauda equina syndrome screening (requires immediate imaging and surgical consultation) 1:
- Urinary retention (90% sensitivity—most frequent finding)
- Fecal incontinence
- Saddle anesthesia
- Bilateral leg weakness
- Note: Without urinary retention, probability of cauda equina is approximately 1 in 10,000
Range of motion assessment: Thoracolumbar rotation, flexion/extension, and fingertip-to-floor distance at 4-week follow-up predict 12-month outcomes better than baseline measurements 2
Psychosocial Risk Factor Assessment
Evaluate psychosocial factors that predict chronic disabling back pain 1:
- Fear-avoidance behaviors
- Catastrophizing
- Depression or anxiety
- Job dissatisfaction
- Pending litigation or disability claims
Imaging Decisions
Do not routinely order imaging for nonspecific low back pain without red flags. 1, 3
Obtain immediate imaging (MRI preferred) only when 1:
- Progressive or severe neurologic deficits at multiple levels
- Suspected cauda equina syndrome
- Strong suspicion for cancer, infection, or fracture based on red flags
Physical Examination Predictors of Outcome
Reassess physical measures at 4 weeks rather than relying solely on baseline examination 2:
- Thoracolumbar rotation at 4 weeks predicts pain intensity at 12 months
- Isometric endurance of back extensors at 4 weeks predicts disability at 12 months
- Fingertip-to-floor distance at 4 weeks predicts functional outcomes
Common pitfall: Approximately 40% of patients report increased pain immediately after physical examination, but this group shows greater improvement in physical measures between baseline and 4-week follow-up 2
Assessment of Multisite Pain
Screen for pain at other musculoskeletal sites, as multisite pain predicts worse functional status, poorer prognosis, and reduced treatment response 4:
- More pain sites correlate with reduced physical and mental function regardless of pain location
- Patients with co-occurring musculoskeletal symptoms require more intensive multimodal management
Muscle Function Assessment in Chronic Cases
For pain persisting beyond 12 weeks, assess back muscle structure and function 5:
- Muscle atrophy (particularly multifidus)
- Reduced muscle endurance
- Altered muscle activation patterns
- These dysfunctions are highly prevalent in chronic low back pain and guide exercise prescription
Common Assessment Pitfalls to Avoid
- Do not assume pain intensity correlates with disease severity—mild pain can represent serious pathology 3
- Do not rely on baseline physical measures alone—4-week reassessment provides superior prognostic information 2
- Do not overlook psychosocial factors—they are stronger predictors of chronicity than physical findings 1
- Do not order imaging for reassurance—it does not improve outcomes in nonspecific low back pain and may lead to unnecessary interventions 1, 3