In September 2006, we investigated a cluster of 9 patients who developed Enterococcus gallinarum infection after total knee arthroplasty. Isolates recovered from these patients were from the same outbreak strain. Although all 9 patients were monitored by the same healthcare personnel, were given spinal anesthesia, and had the same specific type of wound irrigation procedure performed during their hospitalization, the source or sources of these infections were not identified.