It is unknown whether giving pre-operative antibiotics affects the results of intraoperative bacterial cultures. This is an important question as antibiotics are often not given prior to surgery out of concern that accurate culture results will not be obtained. It is important to obtain accurate cultures so that targeted antibiotic therapy can be used. However, delaying the administration of antibiotics also delays the onset of treatment. Currently, the optimal course of action is unknown. The purpose of this study is to resolve this issue and determine if prophylactic antibiotics affect intra-operative culture results in patients undergoing revision hip or knee arthroplasty surgery for infection.