This observational study will target patients with axial spondyloarthritis (axSpA) and psoriatic arthritis (PsA) who have started treatment with bimekizumab, upadacitinib, risankizumab, guselkumab, or a tumour necrosis factor-alpha inhibitor (e.g., adalimumab or etanercept) at NHS hospitals in the United Kingdom. Information from patients' medical records will be collected, and patients will complete surveys about their experiences with their treatment. The study will look at treatment effectiveness from both healthcare professionals' and patients' points of view.