➤ Negative results on culture still pose a real challenge in the diagnosis of periprosthetic joint infection.➤ There are numerous reasons for the inability to isolate the infecting organism from the affected joint, the most important of which is the administration of antibiotics prior to obtaining culture samples.➤ For patients suspected of having a periprosthetic joint infection, antibiotics should not be given until the diagnosis is confirmed or aspiration of the joint should be delayed for at least two weeks after the last dose of antibiotics.➤ Other strategies that can be used to enhance the likelihood of obtaining a positive result on culture include expeditious transport of culture samples, placement of a tissue or fluid sample in the appropriate medium, implant sonication, and prolonging the incubation period of the samples to two or three weeks.➤ In patients in whom the prerevision aspiration has not yielded an infecting organism, yet the clinical picture is consistent with periprosthetic joint infection, a minimum of three to five tissue culture samples are recommended at the time of revision surgery.➤ Biomarkers and molecular techniques, such as polymerase chain reaction identification of bacterial DNA, may play an increasing role in the future in the diagnosis of periprosthetic joint infection, when standardized techniques have not identified an infecting organism.