Two-stage treatment is currently the most common approach for management of an infected joint prosthesis in the United States. Static antibiotic-impregnated polymethylmethacrylate cement spacers have traditionally been used; increasingly, however, mobile or articulating spacers are being utilized. Advocates of mobile spacers have cited potential advantages, including more effective maintenance of the joint space, allowing for limited weight bearing and facilitating joint motion; possible reduction in bone loss; and local delivery of antibiotics. Because a variety of materials and construction methods is used to make knee and hip spacers, comparisons are difficult. Randomized, prospective studies are needed to determine the best spacers for total knee and total hip arthroplasties.