What causes lateral mid back pain?

Lateral Mid Back Pain: Causes and Clinical Approach

Lateral mid back pain (thoracic region) most commonly arises from musculoskeletal sources including facet joint arthropathy, paraspinous muscle strain, rib articulation dysfunction, or costochondritis, but you must systematically exclude serious pathology including vertebral compression fractures, malignancy, infection, and inflammatory conditions before attributing symptoms to benign mechanical causes. 1

Primary Etiologies by Anatomical Location

Vertebral Column Pathology

• Compression fractures are particularly common in the thoracic spine and should be suspected in patients >65 years, those with osteoporosis, or chronic steroid users 1
• Malignancy (primary or metastatic) frequently affects the thoracic spine due to its rich vascular supply; posttest probability increases to 9% with prior cancer history 1
• Discitis/osteomyelitis should be considered with fever, recent infection, IV drug use, or immunocompromised status 1

Lateral Pain-Specific Considerations

• Lateral waist area pain in postmenopausal women increases the risk of vertebral fractures 4.5-fold compared to midline pain alone 2
• Facet joint arthropathy typically presents with paramidline (lateral to spinous processes) rather than midline pain 3
• Rib-related pathology including costochondritis or rib fractures produces lateral thoracic pain 1

Inflammatory Conditions

• Ankylosing spondylitis and other spondyloarthropathies commonly affect the thoracic spine, presenting with morning stiffness >30 minutes that improves with exercise 1
• Consider inflammatory arthritis in younger patients with alternating pain patterns and nighttime awakening 1

Red Flags Requiring Immediate Imaging

Do not delay imaging when any of the following are present: 1

• Neurologic deficits: myelopathy, progressive motor weakness, or radiculopathy 1
• Constitutional symptoms: unexplained weight loss, fever, night sweats 1
• Cancer history: any prior malignancy (excluding nonmelanoma skin cancer) 1
• Age >65 years with acute onset pain (fracture risk) 1
• Chronic steroid use or known osteoporosis 1
• Significant trauma or prior thoracic spine surgery 1
• Failure to improve after 1 month of conservative management 1

Diagnostic Algorithm

Initial Assessment (No Red Flags Present)

• Conservative management for 4-6 weeks is appropriate for uncomplicated acute thoracic back pain without imaging 1
• Maintain activity, avoid bed rest, use simple analgesics or NSAIDs 4
• Physical therapy and fitness programs reduce pain and improve function 4

When to Image (Red Flags or Persistent Symptoms)

• MRI thoracic spine without contrast is the preferred initial study for suspected cord compression, malignancy, or infection 1
• MRI with and without contrast when infection, inflammation, or neoplasm is strongly suspected 1
• CT thoracic spine is superior for evaluating cortical bone, fractures, and facet arthropathy 1
• Radiography may be considered after 6 weeks of failed conservative therapy in low-risk patients 1

Critical Pitfalls to Avoid

Do not obtain routine imaging for uncomplicated thoracic back pain in the first 4-6 weeks—it provides no clinical benefit and leads to unnecessary interventions 1, 5

Do not miss compression fractures in older adults—the thoracic spine is the most common site for osteoporotic fractures, and lateral pain is a strong predictor 1, 2, 6

Do not attribute lateral thoracic pain to "muscle strain" without excluding visceral causes—intrathoracic, renal, vascular, or gastrointestinal pathology can present as thoracic back pain 1

Do not ignore inflammatory markers in younger patients—ankylosing spondylitis and other spondyloarthropathies commonly affect the thoracic spine and require specific treatment 1

Non-Spinal Causes Requiring Consideration

Lateral mid back pain may originate from: 1

• Intrathoracic pathology: pneumonia, pulmonary embolism, pleural disease
• Renal pathology: nephrolithiasis, pyelonephritis
• Vascular pathology: aortic dissection or aneurysm
• Gastrointestinal pathology: pancreatitis, peptic ulcer disease