Immune-mediated polyarthritis causes severe joint pain and swelling in multiple joints simultaneously, significantly reducing mobility and quality of life until effective immunosuppressive treatment is established.
IMPA causes acute, severe welfare harm — dogs in active flare are often unable to walk normally, show profound pain responses on handling, and may refuse to bear weight on severely affected limbs. The multi-joint nature of the disease means that dogs cannot compensate by shifting weight to unaffected limbs as they might with monoarthritis. The welfare trajectory after appropriate diagnosis and treatment can be remarkably positive: most non-erosive IMPA cases respond rapidly to immunosuppression, with dogs returning to comfortable mobility within days. This rapid welfare improvement makes prompt and accurate diagnosis a high-stakes welfare intervention. Prolonged delay in diagnosis — which occurs when IMPA is mistaken for orthopaedic lameness — means extended unnecessary suffering from a highly treatable condition.