BACKGROUND: As the US population ages, the number of hip and knee arthroplasties is expected to increase. Because surgical site infections (SSIs) following these procedures contribute substantial morbidity, mortality, and costs, we projected SSIs expected to occur from 2020 through 2030.METHODS: We used a stochastic Poisson process to project the number of primary and revision arthroplasties and SSIs. Primary arthroplasty rates were calculated using annual estimates of hip and knee arthroplasty stratified by age and gender from the 2012-2014 Nationwide Inpatient Sample and standardized by census population data. Revision rates, dependent on time from primary procedure, were obtained from published literature and were uniformly applied for all ages and genders. Stratified complex SSI rates for arthroplasties were obtained from 2012-2015 National Healthcare Safety Network data. To evaluate the possible impact of prevention measures, we recalculated the projections with an SSI rate reduced by 30%, the national target established by the US Department of Health and Human Services (HHS).RESULTS: Without a reduction in SSI rates, we projected an increase in complex SSIs following hip and knee arthroplasty of 14% between 2020 and 2030. We projected a total burden of 77,653 SSIs; however, meeting the 30% rate reduction could prevent 23,297 of these SSIs.CONCLUSIONS: Given current SSI rates, we project that complex SSI burden for primary and revision arthroplasty may increase due to an aging population. Reducing the SSI rate to the national HHS target could prevent 23,000 SSIs and reduce subsequent morbidity, mortality, and Medicare costs.