Treat-to-target in axial spondyloarthritis — what about physical function and activity?

In patients with axial spondyloarthritis (axSpA), pain, functional and structural impairments, reduced mobility and potential deformity of the axial skeleton are the most prominent health concerns. Limitations in physical function and spinal mobility are caused by both inflammation and structural damage, and therefore restrictions to physical function must be monitored throughout a patient’s life. Consequently, the assessment of physical function is recommended as a key domain in the Assessment of Spondyloarthritis International Society–OMERACT Core Outcome Set. However, in comparison with disease activity, physical function seems to be a relatively neglected target of intervention in patients with axSpA, even though physical function is a major contributor to costs and disability in this disease. This Review aims to reacquaint rheumatologists with the targets for physical function, physical activity and performance by giving guidance on determinants of physical function and how physical function can be examined in patients with axSpA. Physical function is an important contributor towards a patient’s quality of life, but is often neglected in management strategies for axial spondyloarthritis (axSpA). This Review provides guidance on determinants and assessments of physical function in axSpA. Key points Impairments in physical function are among the most prominent health concerns in patients with axial spondyloarthritis (axSpA); their assessment is a key domain in the ASAS–OMERACT Core Outcome Set. The WHO International Classification of Functioning, Disability and Health is the most sophisticated classification system to capture the entire spectrum of functioning and health. Physical function can be assessed using self-report tools for physical function and physical activity, objective measurements of spinal mobility and performance-based tests. Physical function in patients with axSpA is influenced by inflammation and structural damage, as well as by comorbidities, mental health and various contextual factors. Although a combination of pharmacological and non-pharmacological therapy is recommended for the management of axSpA, interventions to improve or maintain function is a relatively neglected target for patients with axSpA. Interventions to improve physical function include strategies to enhance physical activity on a regular basis and physiotherapy interventions, often in combination with pharmacological treatments.