Background <p>Osteotomy around the knee (OAK) is an established joint-preserving procedure for knee osteoarthritis; however, postoperative surgical site infection (SSI) remains a serious complication that may compromise bone healing and functional outcomes. Evidence regarding risk factors for SSI requiring reoperation after OAK is limited. This study aimed to identify perioperative factors associated with SSI requiring reoperation following OAK.</p> Methods <p>This multicenter retrospective study included 247 patients (302 knees) who underwent OAK at one institution and two affiliated hospitals between June 2015 and June 2024. SSI was defined as an infection requiring surgical debridement. Patient demographics, comorbidities, perioperative laboratory data, and surgical variables were evaluated. Factors associated with SSI were identified using Firth’s penalized multivariable logistic regression. Sensitivity analyses were performed after excluding knees that underwent osteotomy for valgus deformity and after restricting the dataset to one knee per patient.</p> Results <p>SSI requiring reoperation occurred in 12 of 302 knees (4.0%). Firth’s penalized multivariable logistic regression identified preoperative skin disease, preoperative liver disease, and postoperative hemoglobin decline as factors independently associated with SSI. These associations remained consistent in sensitivity analyses excluding knees that underwent osteotomy for valgus deformity and restricting the analysis to one knee per patient.</p> Conclusions <p>Preoperative skin disease, preoperative liver disease, and postoperative hemoglobin decline were independently associated with an increased risk of SSI requiring reoperation after OAK. Awareness of these factors may aid perioperative risk assessment and postoperative surveillance. Further prospective studies with larger cohorts are needed to validate these findings and establish clinically applicable strategies for infection risk assessment and prevention.</p>