BACKGROUND: Anemia is a frequent co-morbidity in the elderly patients undergoing hip or knee surgery and is often associated with poor clinical outcomes. Mild to moderate anemia is often treated with intravenous or oral iron supplementation. However, the efficacy and safety of iron supplementation in treating anemia for the elderly patients undergoing hip or knee surgery remains controversial. METHODS: Only prospective, randomized studies that compared iron supplementation with no iron supplementation in the elderly patients undergoing hip or knee surgery were included. Six studies met the inclusion criteria: the target population consisted of patients undergoing hip or knee surgery treated with iron supplementation; the study was a published randomized trial. Each outcome measure tested was assessed for heterogeneity. If significant heterogeneity was present for more than 75%, data from the studies were not combined. If there was no significant heterogeneity (less than 40%), a weighted mean difference (WMD) or combined relative risk was calculated using a fixed effects model, while a random effects model was applied when heterogeneity was within 40% to 75%. RESULTS: Our meta-analysis demonstrated the increase of hemoglobin level in patients undergoing hip or knee surgery with iron supplementation. However, no significant difference on the length of hospital stay, morbidity, 1-mo mortality, the infection rate, the rate and volume of allogeneic blood transfusions, and the adverse drug effects was found between the patients with iron treatment and those without. CONCLUSION: Our meta-analysis suggested that iron supplementation was safe and effective in treating anemia for the elderly patients undergoing hip or knee surgery.