According to the majority of accepted definitions, reactive arthritis (ReA) was a kind of spondyloarthritis (SpA) triggered by an intestinal or urogenital infection. According to a broader definition, every arthritis developed after a mucosal surface infection was considered ReA. There was a scant agreement regarding a working definition, the status of HLA-B27, and even classification criteria for ReA. It might also contribute to the absence of systemic investigations and clinical trials for ReA, limiting therapy recommendations to the opinions of specialists. The development of post-COVID-19 ReA had refocused attention on this mysterious organism. Post-COVID-19 ReA could manifest at any age, appears to impact both sexes equally, and could manifest in many ways. A few had simply tenosynovitis or dactylitis; others had small joint arthritis, SpA phenotype with peripheral or axial involvement, or tenosynovitis or dactylitis. The appearance of post-vaccination inflammatory arthritis was suggestive of a similar mechanism. A global consensus must be reached on whether or not to include all of these conditions under ReA. It would allow homogeneous group investigations on how infections cause arthritis and what predicts chronicity. The outcomes extended beyond ReA and could be generalized to other inflammatory arthritides.