A Longitudinal Analysis of Weight Changes Before and After Total Knee Arthroplasty: Weight Trends, Patterns, and Predictors

Introduction: Longitudinal data on patient trends in body mass index (BMI) and the proportion that gain or lose significant weight before and after total knee arthroplasty (TKA) is scarce. This study aimed to observe patients longitudinally for a two-year period and determine 1) clinically significant BMI changes during the one-year before and one-year after TKA; and 2) identify factors associated with clinically significant weight changes. Methods: A prospective cohort of 5,388 patients who underwent primary TKA at a tertiary healthcare institution between January 2016 and December 2019 were analyzed. The outcome of interests were clinically significant weight changes, defined as a ≥5% change in BMI, during the 1-year preoperative and postoperative periods, respectively. Patient-specific variables and demographics were assessed as potential predictors of weight change using multinomial logistic regression. Results: Overall, 47% had a stable weight throughout the study period (preoperative: 17% gained, 15% lost weight; postoperative: 19% gained, 16% lost weight). Patients who were older (OR=0.95), men (OR=0.47), overweight (OR=0.36), and obese class III (OR=0.06) were less likely to gain weight pre-operatively. Preoperative weight loss was associated with postoperative weight gain one-year after TKA (OR=3.03). Preoperative weight gain was associated with postoperative weight loss one-year after TKA (OR=3.16). Conclusion: Most patients maintained a stable weight before and after TKA. Weight changes during the one-year before TKA were strongly associated with reciprocal rebounds in BMI postoperatively, emphasizing the importance of ongoing weight management during TKA and the recognition of patients at higher risk for weight gain.