Impact of obesity on return to work after total knee arthroplasty

Background Total knee arthroplasty (TKA) is an effective and safe treatment of pain and functional impairment in late-stage knee osteoarthritis (OA). In Denmark, 20% of TKAs are performed in patients &lt;60 years of age who can return to work (RTW) after TKA. However, there is limited knowledge about the rate of RTW in this population. Obesity, a major risk factor for TKA complications in terms of incidence and severity, may affect RTW after TKA. <br/>Aim To investigate the association between body mass index (BMI) and rates of RTW in working-age patients with knee OA undergoing TKA. Furthermore, to explore whether the association varies by sex, age, socioeconomic position (SEP), and history of comorbidities.<br/>Materials and Methods We combined data from the Danish Knee Arthroplasty Registry and the Danish Registry for Evaluation of Marginalization, for labor market status. BMI was grouped as normal (&lt;25), pre-obesity (25-29.9), obesity class 1 (30-34.9), 2 (35-39.9), or 3 (≥40). RTW was defined as full- or part-time RTW within 2 years of follow-up. We estimated cumulative incidence proportions (CIP) of RTW (overall and by BMI-group), considering death and early retirement as competing events. Cox proportional hazards models were used to calculate Hazard Ratios (HRs) adjusting for selected confounders.<br/>Results We included 6,162 patients (41% men), median age 55 years (IQR 6.3) and mean BMI 30.8 (95% CI (CI) 30.7;31). The median time to RTW was 69 days (CI 67.6;70). The CIP of RTW at 1 month was 31% (CI: 30;32), at 3 months was 63% (CI 62;65), at 1 year was 92% (CI 92;93), and at 2 years was 96% (CI 95;96). CIPs for RTW in BMI-groups were similar to the overall CIPs, and HRs in BMI-groups were equal to 1. Stratification by age, SEP and comorbidity did not change HRs. Stratification by sex showed no association between BMI and RTW for women, while men in higher BMI-groups had a tendency to lower rate of RTW (HR for obesity class 2 was 0.9 (CI 0.7;1), HR for obesity class 3 was 0.8 (CI 0.7;1) compared to normal BMI). <br/>Interpretation/Conclusion: 31% of TKA patients RTW within 30 days and over 90% RTW within one year. Obesity was not found to affect RTW, but men in obesity class 2 and 3 may need tailored post-TKA rehabilitation to facilitate RTW.<br/>