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This study investigates how changes in body mass index (BMI) before total knee arthroplasty (TKA) affect surgical outcomes.

May 9, 2026Open Access

Does weight gain from time of indication to date of surgery affect outcomes in total knee arthroplasty?

Key Points

This study investigates how changes in body mass index (BMI) before total knee arthroplasty (TKA) affect surgical outcomes.
Retrospective review of patients undergoing primary unilateral TKA from 2015–2024 with a minimum 90-day follow-up.
Patients classified into three groups based on percent BMI change from surgical booking to TKA date: decrease, 0-5% increase, and >5% increase.
Multivariate regression analyzed risk factors affecting BMI changes.
Group with >5% BMI increase had the longest length of stay (50.3 h vs. 48.6 h for Group 1 and 47.1 h for Group 2; P=0.002).
Lower discharge-to-home rates were noted in the >5% increase group (88.7% vs. 89.8% for Group 1 and 91.7% for Group 2; P=0.014).
No significant differences were found in the rates of 90-day ED visits, readmissions, or revision rates.

Abstract

Abstract Background The impact of body mass index (BMI) on outcomes after total knee arthroplasty (TKA) is a highly debated topic. Our study aims to investigate the implications of BMI changes from the day of surgical booking to the surgery date on perioperative and postoperative outcomes. Methods We retrospectively reviewed patients who underwent elective, primary, unilateral TKA at an urban academic institution from 2015–2024 with a minimum 90-day follow-up. The cohort was classified into three groups by percent BMI change from surgical booking date to TKA date: Group 1, decrease in BMI; Group 2, 0–5% increase in BMI; and Group 3, > 5% increase in BMI. Propensity-score matching (1:1:1) based on age, gender, BMI at surgical booking, and smoking status was performed; perioperative and postoperative outcomes were compared. Multivariate regression analysis evaluated risk factors for interval change in BMI. Results Before matching, 12,990 patients were included, with 39.6% in Group 1, 41.2% in Group 2, and the remaining 19.2% in Group 3. Notably, Group 3 had the longest length of stay (50.3 h vs. 48.6 1 P = 0.002) and the lowest discharge-to-home rates (88.7% vs. 89.8% 1 P = 0.014). No significant difference was seen in 90-day ED visits, 90-day readmissions, or revision rates. Logistic regression of the pre-match cohort found that prolonged surgical booking delays were associated with decreased all-cause revisions (OR = 0.98; P = 0.038), while percent BMI change in this period did not impact revision incidence. Duration of surgical booking delay had no impact on BMI changes in obese patients. Conclusion Our study evaluated preoperative BMI change between surgical booking and TKA, finding that most patients (60.4%) gain weight during this time. While patients with significant BMI increases (> 5%) had longer hospital stays and lower discharge-to-home rates, Percent BMI change during this period did not impact all-cause or septic revision incidence.

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