In September 2011, a 52-year old patient suffering from psoriatic arthritis and being treated for an upper respiratory tract infection, presented to the emergency department of Argos General Hospital with fever and a painful, swollen right knee. He underwent clinical, laboratory and imaging examinations. Initially blood and synovial fluid cultures were negative. After an arthroscopic collection of pus, the culture showed a methicillin resistant Staphylococcus aureus which was sensitive only to daptomycin.