Transarterial Embolization Versus Sham Procedure in Adults With Treatment-Resistant Inflammatory Arthritis of a Single Large Joint

Inclusion Criteria: * Age 18 years or older. * Inflammatory monoarthritis of a large joint (wrist, elbow, shoulder, ankle, knee or hip), fulfilling the ASAS classification criteria for peripheral spondyloarthritis, or diagnosed clinically and on imaging by a rheumatologist when of other aetiology. * Refractoriness to local and pharmacological treatment, defined as failure of both: (a) at least two different non-steroidal anti-inflammatory drugs (NSAIDs) at full dose and for an adequate duration; and (b) at least one intra-articular glucocorticoid injection into the target joint. Patients who have also failed one or more conventional synthetic DMARDs (methotrexate, leflunomide or sulfasalazine) at adequate doses for at least 3 months, and patients with a documented contraindication to starting or continuing systemic immunosuppressive therapy, are also eligible. * Failure of structured physiotherapy. * Pain visual analogue scale (VAS) score of 40 mm or more (0-100 mm scale) at baseline. * Written informed consent. Exclusion Criteria: * Active inflammatory involvement of more than one joint. * Contraindications to angiography: allergy to iodinated contrast medium, severe renal impairment (estimated glomerular filtration rate \<30 mL/min) or uncorrectable coagulopathy. * Intra-articular injection into the target joint within the previous 3 months. * Change in disease-modifying antirheumatic drug (DMARD) therapy within the month before enrollment. * Pregnancy or breastfeeding. * Suspected or confirmed current or previous infection of the target joint. * Known or suspected allergy to porcine gelatin or collagen. * Inability to provide informed consent.