Although spinal pain, almost always in the lower back, is usually the first and most common symptom of axial spondyloarthritis (axSpA), individuals with axSpA may also have pain, stiffness, and limited mobility outside of the spine in areas such as the hips, knees, and heels. Notably, lower back pain can only be clinically defined—that is, it cannot be defined by laboratory tests such as C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR)—making it difficult to establish the underlying cause.1 Spinal pain associated with axSpA usually presents with the following general characteristics2:

  • Occurs in early adulthood (before 45 years of age)
  • Has a gradual onset
  • Lasts longer than three months
  • Is worse after rest (eg, in the morning)
  • Improves with activity
  • Wakes patient up in the second half of the night
  • Is associated with morning stiffness lasting more than 30 minutes
  • Can be associated with buttock pain that alternates between the left and right sides

Patients with suspected axSpA must be assessed closely and carefully. Characteristics and associated features are listed in the following Figure.

Figure: Assessment of Spondyloarthritis International Society (ASAS) axSpA classification criteria3,4

It should be noted that making a diagosis by just “ticking boxes on a checklist” of the ASAS classification criteria without a careful evaluation of the patient means an inappropriate use of these criteria.3,5 Like all classification criteria, the ASAS classification criteria should only be applied to patients with an established diagnosis.3


  1. Braun J. Axial spondyloarthritis including ankylosing spondylitis. Rheumatology (Oxford). 2018;57(6uppl 6):vi1-vi3.
  2. Yu DT, van Tubergen A. Patient education: Axial spondyloarthritis, including ankylosing spondylitis (Beyond the Basics). uptodate.com/contents/axial-spondyloarthritis-including-ankylosing-spondylitis-beyond-the-basics. Accessed August 28, 2019.
  3. Proft F, Poddubnyy D. Ankylosing spondylitis and axial spondyloarthritis: recent insights and impact of new classification criteria. Ther Adv Musculoskelet Dis. 2018;10:129-139.
  4. Rudwaleit M, van der Heijde D, Landewé R, et al. The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection. Ann Rheum Dis. 2009;68:777-783.
  5. Aggarwal R, Ringold S, Khanna D, et al. Distinctions between diagnostic and classification criteria? Arthritis Care Res (Hoboken). 2015;67:891-897.
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