What are the causes of back pain?

Causes of Back Pain

Most back pain (>85%) is nonspecific and cannot be reliably attributed to a specific disease or spinal abnormality, but several specific conditions can cause back pain that requires targeted treatment. 1

Major Categories of Back Pain

Back pain can be classified into three broad categories:

1. Nonspecific back pain (85% of cases)

   • Musculoskeletal in origin
   • Cannot be reliably attributed to a specific anatomical source
   • Often self-limiting with conservative management

2. Back pain associated with radiculopathy or spinal stenosis (7% of cases)

   • Radiculopathy: Compression of nerve roots causing radiating pain
   • Spinal stenosis: Narrowing of the spinal canal causing neurogenic claudication

3. Back pain associated with specific spinal causes (8% of cases)

   • Requires prompt evaluation and specific treatment

Specific Causes of Back Pain

Common Specific Causes

• Herniated disc (4% of cases) - Most common at L4/L5 and L5/S1 levels 1
• Spinal stenosis (3% of cases) - Narrowing of spinal canal causing pseudoclaudication 1
• Vertebral compression fracture (4% of cases) - Common in thoracic spine, especially with osteoporosis 1
• Mechanical back pain (97% of all back pain) - Arising from spinal structures such as bone, ligaments, discs, joints, nerves, and meninges 2

Less Common but Serious Causes

• Malignancy (0.7% of cases) - Risk factors include history of cancer (LR 14.7), unexplained weight loss (LR 2.7), failure to improve after 1 month (LR 3.0), and age >50 years (LR 2.7) 1
• Spinal infection (0.01% of cases) - Including discitis, osteomyelitis, epidural abscess 1
• Ankylosing spondylitis (0.3-5% of cases) - Consider in younger patients with morning stiffness, improvement with exercise, alternating buttock pain 1
• Cauda equina syndrome (0.04% of cases) - Urinary retention is the most sensitive finding (90% sensitivity) 1

Non-Spinal Causes of Back Pain

• Referred pain from internal organs - Including pancreatitis, nephrolithiasis, aortic aneurysm 1, 3
• Systemic illnesses - Such as endocarditis or viral syndromes 1

Red Flags Requiring Urgent Evaluation

• Progressive or severe neurologic deficits - Motor deficits at multiple levels 1
• Bladder or bowel dysfunction - Especially urinary retention 1
• Fever with back pain - Suggesting possible infection 3
• History of cancer with new back pain - Increases probability of cancer from 0.7% to 9% 1
• Unexplained weight loss - Associated with malignancy 1
• Severe, unremitting pain, especially at night - May indicate serious pathology 3

Diagnostic Approach

A practical diagnostic approach involves:

1. Focused history and physical examination to classify patients into one of the three broad categories 1
2. Assessment for red flags that suggest serious underlying conditions 1
3. Neurological examination to assess for radiculopathy or myelopathy 1
4. Consideration of risk factors for specific conditions (cancer, infection, fracture) 1

Imaging Considerations

• No imaging is typically needed for acute (<4 weeks) uncomplicated back pain without red flags 1
• Consider imaging after 4-6 weeks of failed conservative treatment 3
• Early imaging is warranted with red flags, significant trauma, myelopathy, or suspected serious pathology 1

Back pain is a complex symptom that requires careful evaluation to identify potentially serious underlying causes while avoiding unnecessary testing in cases of nonspecific back pain.