What are the key symptoms of axial spondyloarthritis (axSpA)?

Key Symptoms of Axial Spondyloarthritis

The hallmark symptom of axial spondyloarthritis is inflammatory back pain, present in 70-80% of patients, characterized by insidious onset before age 45, morning stiffness, improvement with exercise but not rest, pain occurring at night (particularly in the second half), and alternating buttock pain. 1

Core Clinical Features

Inflammatory Back Pain Characteristics

• Onset before age 40-45 years with chronic duration (≥3 months) 1, 2
• Morning stiffness that is prolonged 1, 2
• Improvement with exercise but no improvement with rest - a distinguishing feature from mechanical back pain 1, 3
• Night pain, particularly awakening in the second half of the night 1
• Alternating buttock pain indicating sacroiliac joint involvement 1, 3
• Insidious onset rather than acute trauma 1, 3

Axial Skeletal Involvement

• Sacroiliac joint pain is typically the initial site of involvement, presenting as lower back/buttock pain 1
• Spinal involvement progresses to affect the thoracic spine and thoracolumbar junction most commonly 1
• Chronic back pain and stiffness leading to progressive loss of spinal mobility 1, 2

Associated Musculoskeletal Manifestations

Peripheral Joint and Entheseal Symptoms

• Peripheral arthritis affecting large joints (most commonly knees) in an oligoarticular, asymmetric pattern occurs in 30-50% of patients 1, 2
• Enthesitis (inflammation at tendon insertion sites) is a characteristic feature 2, 3
• Dactylitis (sausage-like swelling of digits) may occur 3

Extra-Articular Manifestations

Systemic Features

• Uveitis (inflammatory eye disease) is a common extra-articular manifestation 1, 2, 3
• Psoriasis occurs in association with axSpA 1, 2, 3
• Inflammatory bowel disease may be present 1, 2

Clinical Pearls for Recognition

Diagnostic Clues

• Good response to NSAIDs is characteristic of inflammatory back pain 3
• HLA-B27 positivity is present in 74-89% of patients, though not diagnostic alone 1
• Elevated inflammatory markers (C-reactive protein) may be present but are not always elevated 1, 2
• Family history of spondyloarthritis increases suspicion 3

Important Caveats

The diagnosis is frequently delayed by 4.9 to 8 years from symptom onset, highlighting the challenge of early recognition 1, 2. Inflammatory back pain symptoms are present in 5-6% of the general adult population and up to 15% in primary care settings, so additional features beyond back pain alone are needed to establish the diagnosis 1. Not all patients present with the classic bilateral sacroiliitis pattern - psoriatic spondyloarthritis may cause unilateral sacroiliitis, and a minority have isolated spine involvement without sacroiliac joint disease 1.

Pain Pattern Evolution

While inflammatory back pain is the primary symptom, pain in axSpA can evolve to include structural causes from new bone formation, vertebral fractures (increased risk in longstanding disease), and degenerative changes 4. Changes in the nature of reported back pain warrant careful re-evaluation for alternative causes 4.