Purpose The preferred radionuclide imaging procedure for diagnosing prosthetic joint infection is combined radiolabeled leukocyte/$^{99m}Tc$ sulfur colloid bone marrow scintigraphy, which has an accuracy of over 90 %. Unfortunately, sulfur colloid is no longer available in South Korea. In this study, we evaluated the usefulness of $^{99m}Tc$ phytate, a substitute for $^{99m}Tc$ sulfur colloid, when combined with radiolabeled leukocyte scintigraphy in suspected prosthetic knee infections. Methods Eleven patients (nine women, two men; mean age $72{pm}6$ years) with painful knee prostheses and a suspicion of infection underwent both $^{99m}Tc$ HMPAO leukocyte scintigraphy (LS) and $^{99m}Tc$ phytate bone marrow scintigraphy (BMS). The combined images were interpreted as positive for infection when radioactivity in the LS at the site of clinical interest clearly exceeded that of the BMS (discordant); they were interpreted as negative when the increased activity in the LS was consistent with an increased activity in the BMS (concordant). The final diagnosis was made with microbio-logical or intraoperative findings and a clinical follow-up of at least 12 months. Results Five of eleven patients were diagnosed as having an infected prosthesis. The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of the combined LS/BMS were 100 %, 83 %, 83 %, 100 % and 91 %, respectively. Conclusion We find that combined $^{99m}Tc$ HMPAO LS/$^{99m}Tc$ phytate BMS shows comparable diagnostic performance to other studies utilizing sulfur colloid. Combined $^{99m}Tc$ HMPAO LS/$^{99m}Tc$ phytate BMS is therefore expected to be an acceptable alternative to combined radiolabeled LS/$^{99m}Tc$ sulfur colloid BMS for diagnosing prosthetic knee infections.