Infection of a total joint replacement with Mycobacterium tuberculosis is uncommon in North America. This case describes a staphylococcal superinfection that masked an underlying tuberculous infection after total knee replacement and subsequent placement of a cement spacer. The patient had no evidence of M tuberculosis infection elsewhere. The most common explanation for these events is local reactivation of quiescent tuberculosis of the knee joint. The patient was treated successfully with surgical débridement, arthrodesis, and antituberculous medication.