Katakam A, Bragdon CR, Chen AF, et al. - This study was performed with the following aims: (1) to determine the correlation between body mass index (BMI) and failure to achieve the 1-year Knee Disability and Osteoarthritis Outcome Score-Physical Function Short Form (KOOS-PS) minimal clinically important difference (MCID) for total knee arthroplasty (TKA) patients and (2) to ascertain the body mass index (BMI) threshold, if any, beyond which the risk of failing to achieve the MCID is significantly increased. Researchers queried a regional arthroplasty registry identifying 1,059 TKAs for inclusion in this analysis. Observations revealed correlation of elevated BMI with an increased risk of failure to achieve the 1-year KOOS-PS MCID following TKA. Categorical analysis of BMI indicated that “Overweight” (25-30 kg/m ²), “Obese Class I” (30-35 kg/m ²), “Obese Class II” (35-40 kg/m ²), and “Obese Class III” (>40 kg/m ²) patients were at 77%, 76%, 83%, and 106% higher risk, respectively, of failing to attain the KOOS-PS MCID compared with “Normal BMI” (< 25 kg/m ²) patients.