What clinical features should I assess to differentiate ankylosing spondylitis from other causes of back pain?

Assess for inflammatory back pain features, such as:

• Waking during the second half of the night due to symptoms (recommendation 1.1.5) ¹
• Buttock pain (recommendation 1.1.5) ¹
• Improvement with movement (recommendation 1.1.5) ¹
• Improvement within 48 hours of taking NSAIDs (recommendation 1.1.5) ¹

Additional features include:

• Onset of back pain before the age of 45 years, especially before 35 years (recommendation 1.1.5) ¹
• Presence of current or past arthritis, enthesitis, or psoriasis (recommendation 1.1.5) ¹
• Family history of spondyloarthritis or psoriasis (recommendation 1.1.5) ¹

Signs suggestive of axial spondyloarthritis:

• Back pain starting before age 35 (recommendation 1.1.5) ¹
• Symptoms that wake the patient during the night (recommendation 1.1.5) ¹
• Buttock pain (recommendation 1.1.5) ¹

Additional clinical features that may help differentiate include:

• Presence of dactylitis (recommendation 1.1.9) ¹
• Enthesitis, especially if persistent, in multiple sites, or associated with other features such as uveitis or psoriasis (recommendation 1.1.10) ¹