Obesity is Associated with Greater Improvement in Patient Reported Outcomes Following Primary Total Knee Arthroplasty.

BACKGROUND: Body mass index (BMI) cutoffs have been established for total knee arthroplasty (TKA) patients due to increased risk of medical complications in obese patients. However, evidence-based medical optimization may mitigate risk in these patients. This study examined the influence of BMI on patient-reported outcomes measures (PROMs) following primary TKA with specialized perioperative optimization. METHODS: Between 2016 and 2020, 1,329 consecutive primary TKAs using standardized perioperative optimization were retrospectively reviewed. Patients were categorized into ordinal-groups based on BMI in 5kg/m2 increments (range, 17 to 61). Primary outcomes related to activity level, pain, function, and satisfaction were evaluated. BMI groups ≥35 had significantly lower age, more women, and higher prevalence of comorbidities (P≤0.004). Mean follow-up was 1.7 years (range, 1 to 5). RESULTS: Each successive BMI group from 35 to ≥50 demonstrated continually greater improvement in pain with level walking and stair climbing (P≤0.001); Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (P=0.001); and greater satisfaction (P=0.007). Patients who had a BMI <30 had greater final University of California-Los Angeles Activity Levels compared to other groups (P<0.001). No patients who had a BMI ≥35 were revised for aseptic loosening, and rates of periprosthetic joint infection were not different between BMI groups (P=1.000). CONCLUSION: Despite being more debilitated preoperatively, patients who had a BMI ≥35 experienced greater improvement in PROMs compared to patients who had lower BMI. Given the significant improvements in PROMs and quality of life in obese patients; with appropriate perioperative optimization, these patients should not be prohibited from having TKA when appropriately indicated.