Varicella-zoster virus-associated arthritis has not been well documented in adults. We present the case of a 27-year-old female patient with monoarthritis of the knee associated with clinical symptoms typical of varicella. Arthroscopic examination showed unusual oval and circular lesions in cartilage, some of which measured 5 +/- 3 mm in diameter in weight-supporting zones. Such lesions have not been described previously and were type III-A lesions on the Noyes scale or grade IV on the Outerbridge scale. On microscopic observation, synovial fluid cultures and hemocultures were negative for the presence of bacteria. A biopsy sample and synovial liquid from the affected knee produced a positive polymerase chain reaction for varicella-zoster virus, genotype E. These findings suggest a strong relation between clinical varicella infection and important lesion invasion in the knee articulation of such a young adult, probably related to the virus. However, it remains necessary to corroborate this relation between cartilage destruction and clinical symptoms of varicella associated with monoarthritis of an adult knee. Nevertheless, it is advisable to initiate the appropriate antiviral treatment in adults with varicella-related gonalgia because the lesions produce the most severe effects on exposure to the knee bone.