Monoarthritis as the presenting manifestation of localized Ewing's sarcoma in an older patient.

Monoarthritis, infrequently recognized as a manifestation of primary malignant disease of the bone, is rarely associated with Ewing's sarcoma. Our patient presented with knee monoarthritis, and histology established the diagnosis of Ewing's sarcoma. His disease apparently remitted with chemotherapy but recurred in multiple sites one year later, and repeat chemotherapy failed to produce a remission.