Patient factors associated with weight gain and weight loss after knee or hip arthroplasty

Objectives: Following total knee or total hip arthroplasty (TKA, THA), up to 31% of recipients experience significant weight gain while up to 14% experience significant weight loss. Factors associated with significant weight change (≥5% of baseline weight) have not been comprehensively explored. This study aimed to identify pre- and post-surgical (including current) patient factors associated with significant weight change three years after surgery. Methods: A pre-existing nationally-acquired cohort who underwent TKA or THA for osteoarthritis participated in 3-year telephone follow-up. Updated weight, comorbidity, and complication data were collected along with ongoing index joint problems and other patient-reported outcomes including global improvement. These data, along with body mass index (BMI) pre-surgery and post-surgery rehabilitation received, were incorporated into two multivariable logistic regression models to determine separately the factors associated with ≥5% weight gain and ≥5% loss at 3-years post-surgery. Results: 73.4% (1289/1757) participated in the follow-up; 1191 (n = 663 TKA) provided updated weight data. Patterns of weight change were similar for both surgeries (TKA: 16.1% gained ≥5%, 19.6% lost ≥5%; THA: 15.8% gained ≥5%, 17.8% lost ≥5%). In multivariable modelling, younger age and lower pre-surgery BMI were significantly associated with weight gain; female gender and an absence of ongoing index joint issues were associated with weight loss. Conclusion: Different mechanisms are likely associated with significant weight gain or loss at 3-years post-surgery. Cogent weight management entails consideration of both outcomes. Many post-surgical factors appear not to be importantly associated with weight change.