Does inflammatory back pain cause pain when bending?

Inflammatory Back Pain and Bending

Inflammatory back pain characteristically improves with exercise and movement, including bending, rather than worsening with it—this is a key distinguishing feature from mechanical back pain. 1, 2

Core Clinical Features of Inflammatory Back Pain

The defining characteristics of inflammatory back pain (IBP) that distinguish it from mechanical causes include 1, 2:

• Improvement with exercise and movement (not worsening)
• Pain at night that may wake the patient
• Morning stiffness lasting >30 minutes
• No improvement with rest (often worsens)
• Insidious onset before age 40 years

Pain Response to Bending: The Critical Distinction

Inflammatory Back Pain Pattern

• Bending and exercise typically provide relief rather than exacerbation 1, 2
• Movement helps reduce stiffness and pain in inflammatory conditions 1
• The hallmark is that activity improves symptoms while rest worsens them 2

Mechanical Back Pain Pattern (The Opposite)

Mechanical back pain demonstrates the inverse pattern 3:

• Pain with lifting, bending forward, and repetitive movements are moderate-to-strong indicators of mechanical etiology 3
• Pain develops or worsens later in the day with accumulated activity 3
• Pain with specific movements like trunk flexion, getting out of chairs, or prolonged standing 3

Clinical Application

When evaluating a patient with chronic back pain 1, 4:

If pain worsens with bending: This suggests mechanical rather than inflammatory etiology, particularly if accompanied by pain with lifting, prolonged standing, or repetitive activities 3

If pain improves with bending/exercise: This supports inflammatory back pain, especially when combined with night pain, morning stiffness >30 minutes, and age of onset <40 years 2

Diagnostic Threshold

The ASAS expert criteria require at least 4 out of 5 parameters for IBP diagnosis (sensitivity 79.6%, specificity 72.4%) 2:

1. Improvement with exercise
2. Pain at night
3. Insidious onset
4. Age at onset <40 years
5. No improvement with rest

Important Caveat

IBP is a clinical concept for referral and screening, not a diagnosis itself 4. The presence of IBP features should prompt evaluation for axial spondyloarthritis through imaging (radiographs of sacroiliac joints initially, followed by MRI if negative) and HLA-B27 testing 1. Only 5-10% of patients with chronic back pain have inflammatory causes 5, but delayed diagnosis leads to worse outcomes 4.