Axial spondyloarthritis

The spondyloarthritides are a group of inflammatory conditions which can affect axial or peripheral joints.

Axial spondyloarthritis

  • Radiographic axial spondyloarthritis*
  • Non-radiographic axial spondyloarthritis**

*This is the entity that used to be known as ankylosing spondyloarthritis. However, the criteria for diagnosing AS included X-ray changes, which don’t show up for several years, which meant opportunities for early management were getting missed.

**Changes in non-radiographic axial spondyloarthritis can be seen on MRI scan, but not on X-ray.

Peripheral spondyloarthritis

  • Psoriatic arthritis
  • Reactive arthritis
  • Enteropathic spondyloarthritis

The division isn’t clear-cut; axial spondyloarthritis can have occasional peripheral manifestations, and vice versa.


The spondyloarthritides are, apparently, tricksy buggers when it comes to diagnosing them (yes, I’m paraphrasing the actual NICE guidelines). There are a wide range of possible early symptoms, and no single sign, symptom, or finding can rule them in or out; and, yes, that includes our old friend HLA B27, because people with axial spondyloarthritis can be negative for this. X-rays of SI joints can likewise be normal.

Prevalence of axial spondyloarthritis is in fact roughly equal between women and men. However, presentations in women tend to be milder and more atypical and thus are more often missed.

The most common presentation is low back pain. Typically, this:

  • Has an insidious onset; the patient will struggle to remember exactly when it started.
  • Is improved by activity (note that this can also be the case for mechanical back pain).

Note that when taking a history where inflammatory pain is suspected, you should ask about a past history of other joint pains, possible psoriatic rashes, and red eyes; remember some of these problems might have happened years earlier and not be readily recalled.

Features of inflammatory back pain

Pain is considered inflammatory in nature if it’s lasted >3/12 in an under-50 and has at least two of the following four features:

  • Eased by activity but not by rest
  • Morning stiffness >30 mins
  • Waking in the second half of the night with the pain
  • Buttock pain, alternating sides

Atypical presentations

Be aware that:

  • The pain might be in the mid-thoracic area, chest, or neck rather than the lower back. (Chest pain can be caused by the involvement of costovertebral joints, or by enthesitis, which is inflammation of the insertion sites of ligaments/tendons.)
  • The person might present with mild constitutional symptoms; low-grade fever, reduced appetite, fatigue, poor sleep, malaise

Peripheral joint involvement

This can occur; more commonly so in children, psoriatic spondyloarthritis, or spondyloarthritis associated with IBD.  It presents as:

  • Asymmetric
  • Mainly in knees/hips. (Heel pain can occur due to enthesitis of the Achilles tendon.)
  • Oligoarticular; i.e., in fewer than three joints.

Acute anterior uveitis

This occurs in a high percentage of patients with spondyloarthritides (between 25 and 40%) and is, of course, important not to miss. Symptoms include:

  • Acutely painful red eye
  • Photophobia
  • Increased lacrimation
  • Sometimes, blurred vision

Possible signs include:

  • Circumcorneal congestion
  • Small pupil
  • Swollen iris
  • Exudate

Patients should be seen same day by an ophthalmologist (delay risks formation of adhesions, which increase the risk of later glaucoma).


When examining patients with suspected inflammatory back pain, use the modified Schoberâs test:

  • Find the midpoint of the line between the dimples of Venus (posterior superior iliac spines)
  • Mark points 10 cm vertically above this and 5 cm vertically below, with the person standing upright
  • Get the person to bend forwards as far as possible, and measure the distance between those two points again.

Extension should be >5 cm (i.e., the distance between the points should be 20 cm or more when in full flexion).

Other things to check for:

  • Tenderness over SI joints
  • Tenderness over entheses; check spinous processes, anterior chest wall, iliac crests, ischial tuberosities, greater trochanters, Achilles tendon insertion sites, plantar fascia.
  • Signs of psoriasis (don’t forget nail changes) or of anterior uveitis.

Criteria for referral

For suspected axial spondyloarthritis, refer if the person is under 45, the pain has lasted for >3/12, and at least four of the following are present:

  • The pain started before age 35
  • Waking in the second half of the night with pain
  • Buttock pain
  • Improvement with movement
  • Improvement within 48 hrs of taking NSAIDs (which seems pretty broad to me; taking a painkiller is going to improve a lot of cases of pain)
  • 1st-degree relative with spondyloarthritis
  • Any history of enthesitis
  • Any history of arthritis
  • Any history of psoriasis

If the person has only three of the four criteria, check HLAB27: if positive, that can act as a tie-breaker. If the person still falls short of the criteria, advise them to come back if new signs or symptoms.

There are also quite a lot of possible criteria regarding referral for people with acute inflammatory arthritis, dactylitis, suspected psoriatic arthritis, or enthesitis. Overall, note this helpful infographic.

Where criteria are fitted, the recommendation is usually to refer without doing investigations. This includes imaging, which should be left to secondary care; however, just in case I get someone coming in arranging a private scan before getting seen (rare but not impossible), it’s important to note that the request for MRI scans should request the MRI protocol for spondyloarthritis, as there are specific views wanted.

Associated long-term risks

Note that patients are at increased risk of

  • Cardiovascular disease – screen for other risk factors
  • Osteoporosis – refer for bone density screening. Consider balance training to reduce falls risk.
  • Infection – make sure they get flu jabs and pneumonia jabs (remember not to use live vaccines if they’re immunocompromised). Also, note the risk of pneumonia due to reduction in chest expansion.



About Dr Sarah

I'm a GP with a husband and two young children.
This entry was posted in Back pain, Musculoskeletal, Rheumatology. Bookmark the permalink.

1 Response to Axial spondyloarthritis

  1. Pingback: Red flags in low back pain | A Spoonful Of Sugar

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