MD Notes

creation date: 2025-07-16 02:33
tags: Workups

Low Back Pain

Background

Low back pain is common and present at some point in most adult’s lives. In most cases, episodes are self-limiting.

  • Acute: 4 weeks
  • Subacute: 4-12 weeks
  • Chronic ≥12 weeks

Differential Diagnosis

In majority of cases (>85%) , the diagnosis is mechanical back pain (aka nonspecific back pain). This is the diagnosis of exclusion after ruling out alternative diagnoses. These include:

  • Muscle strain
  • Ligament sprain
  • Discogenic pain
  • Disc herniation
  • Spondylolysis
  • Spondylolisthesis
  • Apophyseal injury
  • Facet joint arthropathy

Urgent, acute diagnoses, although rare, must be considered:

Neurological

  • Spinal cord compression
  • Cauda equina syndrome (compression/spinal canal narrowing below conus medullaris)
  • Lumbosacral radiculopathy (incl. sciatica)
    Infection
  • Vertebral osteomyelitis (and discitis)
  • Spinal epidural abscess
    Fracture
  • Vertebral compression fracture
    Tumour
  • Metastatic cancer of the vertebrae (commonly: prostate, breast, kidney, thyroid, lungs)
    Inflammation

Additionally, in the older population, consider abdominal aortic aneurysm.

Initial Evaluation

History

As mechanical back pain is the presumptive diagnosis, history should focus on identifying suspicious features suggestive of serious etiologies.

Timing:

  • Acute, rapidly progressive pain suggests urgent/acute etiology
  • Gradual onset and/or intermittent pain may be less emergent (eg. OA, spinal stenosis, inflammatory arthritis)

Character and location:

  • Burning pain suggests nerve root distribution (lumbar radiculopathy)
  • Local tenderness to percussion suggests vertebral osteomyelitis, discitis, metastatic disease
  • Pain from ambulation and alleviated with rest suggests OA - spinal stenosis may present similarly with more lower extremity pain
  • Pain and stiffness that is worse in the morning and with rest but improved with exercise suggests axial spondyloarthritis or inflammatory arthritis
  • Primary pain in hip, pelvis, or buttocks suggest referred pain (nonspinal etiology)

Associated symptoms:

  • Acute fecal/urinary incontinence or urinary retention, progressive weakness or falls, saddle anesthesia, or other sensory changes suggests spinal cord compression
  • Fever, chills, and malaise suggests infection
  • Constitutional symptoms, including unintentional weight loss and night sweats, suggests malignancy
  • Extra-articular features (eg. uveitis, IBD) may be associated with spondylarthritis
  • Psychosocial symptoms may be associated with chronic pain

Past medical history:

  • Injection drug use, recent bacteremia, recent epidural, or spinal procedure suggests epidural abscess or vertebral osteomyelitis
  • Smoking or personal/family history of cancer especially PBKTL suggests skeletal metastatic disease.
  • Osteoporosis, prolonged glucocorticoid use, recent trauma suggests vertebral compression fractures

An assessment of psychogenic element may be warranted. This consist of the Waddell’s signs which are associated with maladaptive coping and poorer outcomes:

  • Superficial and non-anatomic tenderness
  • Axial loading (press downwards on head while standing) and acetabular rotation (rotate shoulder anad pelvis passively)
  • Distracted straight leg raise discrepancy (less pain when distracted)
  • Regional sensory disturbance (non-dermatomal pattern) and regional weakness (non-neuroanatomical)
  • Overreaction (not reproduced with later stimulus)

An assessment of “yellow flags” for long-term chronicity and disability should be made:

  • Negative attitude that back pain is harmful or potentially severely disabling
  • Fear avoidance behaviour and reduced activity levels
  • An expectation that passive treatment will be beneficial as opposed to active
  • Tendency for depression, low morale, and social withdrawal
  • Social or financial problems

Physical Exam

Inspect the back and posture for abnormalities such as scoliosis or hyperkyphosis. Palpate and percuss the back for vertebral or soft tissue tenderness.

A neurologic exam should evaluate reflexes, strength, sensation, and gait.

Red Flags

To summarize, the following findings should raise suspicion for serious etiology:

  • Thoracic pain
  • Fever and unexplained weight loss
  • Bladder or bowel dysfunction
  • History of malignancy
  • Ill health or presence of comorbidities
  • Progressive neurological deficit
  • Disturbed gait, saddle anaesthesia
  • Age of onset <20 years or >55 years

Investigations

Further investigations are not required for nonspecific back pain without any suspicion for serious etiology.

Suspected cauda equina syndrome:

  • Emergency MRI and consult

Suspected malignancy:

  • ESR and/or CRP
  • Pain radiograph
  • MRI if radiograph normal but ESR or CRP elevated

Suspected spinal infection:

  • MRI if moderate to high suspicion
  • ESR and/or CRP if low suspicion

Suspected vertebral compression fracture:

  • Plain radiograph

No improvement after conservative therapy for nonspecific back pain in 4-6 weeks:

  • Plain radiograph

References

Tools / Guidelines

Additional Reading

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