We report a 68-year-old woman presenting with pain and swelling in her left elbow. An elbow magnetic resonance with gadolinium evidenced bone marrow infiltration and a bone infarct. Given these findings, a body CT scan was performed which showed multiple mesenteric adenopathies and a large retroperitoneal mass. A lymph node biopsy confirmed a B cell lymphoma. Monoarthritis with no systemic manifestations represents a highly uncommon form of presentation of lymphoma. Moreover it usually affects inferior limbs, particularly in the presence of bone infarction.