Magnetic Resonance Imaging in Axial Spondyloarthritis: Beyond the Sacroiliac Joints—Focus on Facet Joint Involvement

Background

Axial spondyloarthritis (axSpA) is a chronic inflammatory disease of the sacroiliac joints (SIJs) and spine, encompassing non-radiographic axSpA (nr-axSpA) and radiographic axSpA (r-axSpA) or ankylosing spondylitis (AS). Early diagnosis is challenging, particularly in nr-axSpA, due to the absence of radiographic sacroiliitis and overlap with nonspecific back pain. Imaging plays a pivotal role in disease classification and monitoring.