Spondyloarthritis (SpA) is a descriptive term which refers to a group of chronic immune-mediated rheumatic diseases, affecting the axial skeleton (spine and pelvis) and the peripheral joints. Typical clinical signs and symptoms are inflammatory back pain, arthritis (i.e. joint swelling), enthesitis (i.e. inflammation at the site where a tendon attaches to the bone, typically the Achilles tendon) and dactylitis (i.e. a fusiform swelling of fingers or toes). In addition, extra-articular manifestations such as psoriasis, uveitis and inflammatory bowel disease (IBD, Crohn’s disease or ulcerative colitis) also belong to the SpA concept. Although the clinical presentation might be heterogeneous, SpA patients usually share some clinical, genetic, laboratory and radiological features. Currently available treatment options include several types of disease modifying anti-rheumatic drugs (DMARDs) as well as symptomatic therapy with non-steroidal and steroidal anti-inflammatory drugs, which should be used in accordance with the patient’s profile (axial, peripheral, extra-articular manifestations). SpA usually affects young people (3th– 6th decade) and potentially has severe implications for physical and psychosocial functioning.    

The Assessment of Spondyloarthritis International Society (ASAS) currently subdivides SpA patients in two groups,  patients with a predominant axial (axSpA) or predominant peripheral clinical presentation (pSpA), which is useful from a clinical point of view but also from a research perspective.2,3 The pathogenesis of SpA consists of a complex interplay between genetic, environmental, immunopathological and biomechanical factors, with some specificities for axial and peripheral disease. Each of these factors contribute to a triad of hallmark features, namely inflammation, bone destruction and new bone formation. Animal models demonstrated a potential role for biomechanical stress in the pathogenesis of entheseal and joint inflammation.4 Unlike these preclinical models, which focused on peripheral joints and entheses, clinical research and imaging studies have primarily addressed the relationship between biomechanical stress and spinal inflammation (axSpA).5 Its role in the pathogenesis of human peripheral SpA is however poorly studied.

Preliminary data from a Belgian nationwide inception cohort (Be-Giant, BelGian Inflammatory Arthritis and spoNdylitis CohorT) indicate that patients with peripheral SpA usually present with asymmetrical arthritis, which may be oligo-articular (<5 joints involved) or polyarticular (≥ 5 joints involved). Interestingly, limb dominancy proved to be a predictor for arthritis counts at the ipsilateral side, especially in the upper limbs. In other words, right-handed patients tend to have more arthritis at joints of the right upper limb, whereas arthritis in left-handed patients is more frequently found in the left upper limb. These clinic">