Reactive arthritis is a form of inflammatory joint disease triggered by an infection elsewhere in the body rather than by direct infection of the joint itself. The classic triggers are certain foodborne bacteria, including Salmonella, Shigella, Campylobacter, and Yersinia, as well as sexually transmitted infections such as Chlamydia. Days to weeks after the infection, the immune system’s response misfires and attacks the joints, typically the knees, ankles, and feet, sometimes with eye inflammation and urinary symptoms in the classic triad. Most people recover within months, though some develop chronic arthritis. People carrying the HLA-B27 gene are markedly more susceptible. It is a reminder that food poisoning can have consequences reaching far beyond the gut.