What are the possible causes of back pain?

What Could Cause Back Pain

Back pain has three broad diagnostic categories: nonspecific mechanical low back pain (>85% of cases), back pain with radiculopathy or spinal stenosis, and back pain with specific underlying pathology such as infection, malignancy, or inflammatory disease. 1

Nonspecific Mechanical Low Back Pain (Most Common)

This accounts for over 85% of presentations in primary care and includes muscle strain, ligamentous injury, and myofascial pain. 1

• Pain worsens with activity and improves with rest, distinguishing it from inflammatory causes 1
• Mechanical disorders arise from spinal structures including bone, ligaments, discs, joints, nerves, and meninges 2
• Degenerative disc disease is the primum movens of mechanical back pain, with disc degeneration leading to altered mechanical properties and subsequent degenerative arthritis in intervertebral joints 3

Back Pain with Radiculopathy or Spinal Stenosis

Herniated disc with radiculopathy presents with sciatica in a lumbar nerve root distribution and has a prevalence of approximately 4% in primary care. 1

• Spinal stenosis causes pseudoclaudication (leg pain with walking or standing relieved by sitting) with a prevalence of approximately 3% 1
• Degenerative changes including osteophytes and disc space narrowing can lead to foraminal or spinal canal stenosis 3
• Most patients improve within the first 4 weeks with noninvasive management 1

Back Pain with Specific Underlying Pathology (Red Flags)

Inflammatory Causes

Ankylosing spondylitis/axial spondyloarthritis has a prevalence of 0.3-5% in chronic low back pain patients and presents with morning stiffness >30 minutes that improves with movement and worsens with rest. 1, 4

• Improvement with exercise is pathognomonic for inflammatory spondyloarthropathy 4
• Alternating buttock pain and awakening during the second part of the night are characteristic features 4
• Typically presents in younger patients (<45 years) 1

Malignancy

Vertebral malignancy has a prevalence of approximately 0.7%, but history of cancer increases posttest probability to 9%. 1, 5

• Red flags include history of cancer (positive likelihood ratio 14.7), unexplained weight loss, failure to improve after 1 month, and age >50 years 5
• Metastasis is the most frequent cause, while plasmocytoma is the most common primary bone tumor of the spine 3

Infection

Spinal infection has a prevalence of 0.01% and presents with fever, recent infection, IV drug use, or immunocompromised status. 1, 5

• In children aged 2-12 years, spine infections are particularly common with a 3:1 male predominance 6
• Vertebral osteomyelitis and discitis are the most common locations, presenting with persistent nighttime pain, low-grade fever, decreased range of motion, and localized tenderness 6
• Laboratory values typically show leukocytosis, elevated ESR, and elevated CRP 6

Vertebral Compression Fracture

Vertebral compression fractures have a prevalence of 4%, particularly in patients with osteoporosis or steroid use. 1, 5

• Pain is secondary to fractures related to metabolic bone disease 3

Cauda Equina Syndrome

Cauda equina syndrome has a prevalence of 0.04% and presents with urinary retention, fecal incontinence, saddle anesthesia, and motor deficits at multiple levels. 1, 5

• This requires immediate MRI rather than the usual 4-6 week waiting period 1

Pediatric-Specific Causes

In children, the most common etiologies are benign (muscle strain, spondylolysis/spondylolisthesis, disc herniation), but serious diagnoses including infection, neoplasm, and inflammatory diseases must be excluded. 6

• Persistent nighttime back pain refractory to conservative management is present in 25-30% of children with spinal neoplasm 6
• Intramedullary tumors account for 35-40% of intraspinal tumors, with astrocytoma (45-60%) and ependymoma (30-35%) being most common 6
• Juvenile idiopathic arthritis most commonly affects the cervical spine in late childhood 6

Common Pitfalls to Avoid

• Do not routinely obtain imaging in nonspecific low back pain without red flags, as this does not improve outcomes and may lead to unnecessary interventions 1
• Do not delay imaging when red flags are present—immediate MRI is indicated rather than waiting 4-6 weeks 1, 5
• Do not overlook inflammatory causes in younger patients (<45 years) with chronic symptoms and morning stiffness, as early diagnosis allows for TNF-blocking agents which show strong efficacy when disease duration is <10 years 1
• Do not underestimate cancer risk in patients with prior malignancy—posttest probability increases from 0.7% to 9% 1, 5