The pathogenesis of prosthetic joint infection is related to microorganisms growing in biofilms, rendering these infections difficult to diagnose and to eradicate. Low-grade infections in particular are difficult to distinguish from aseptic failure, often presenting only with early loosening and persisting pain, or no clinical signs of infection at all. A combination of preoperative and intraoperative tests is usually needed for an accurate diagnosis of infection of prosthetic joint infections. Successful treatment requires adequate surgical procedure combined with long-term antimicrobial therapy, ideally with an agent acting on adhering stationary- phase microorganisms. In this article, epidemiology, pathogenesis, diagnosis and treatment of prosthetic joint infections are reviewed.