Apart from systemic symptoms of viral infection parvovirus B19, the infectious agent in erythema infectiosum, can lead to mainly self-limited acute and chronic arthropathy. Because mild subclinical features of the disease can be easily overlooked, joint affections might appear as isolated symptoms. We here report two cases of chronic monoarthritic symptoms of unknown origin, where immunohistochemical detection of B19-positive lymphocytic cells in the synovial tissue led to the diagnosis of B19 arthropathy. In conclusion, respective virus diagnostics should be considered even in chronic monosymptomatic arthritic lesions. The pathology of B19 arthropathy seems to be due to direct virus infection of cells within the synovia.