Although the health-related quality of life (HRQL) for patients who are obese seems to improve after TKA, the magnitude of improvement and the associated factors remain controversial. We previously found body mass index was not associated with changes in HRQL after TKA.

The purposes of this secondary analysis were to determine which patient characteristics and surgical factors were associated with worse health status after TKA in patients who are severe or morbidly obese.

We assessed 60 patients (53 females; mean age, 70 years) 12 months after surgery. The mean number of comorbidities was 2.5. Mean lower limb anthropometric index scores were: suprapatellar, 1.6; infrapatellar, 2; and suprapatellar/infrapatellar, 1.2. Intraoperative difficulty (IOD) was Grade 0, 40%; Grade 1, 48%; and Grade 2, 12%. Ten patients (17%) had complications. We measured HRQL using the disease-specific WOMAC questionnaire. Patient characteristics (sociodemographic variables, BMI, comorbidity, lower limb anthropometry) and surgical factors (IOD, complications, postoperative medical data) were collected. Associations between WOMAC dimension scores at 12 months and patient characteristics and surgical factors were analyzed using linear regression models.

Factors associated with worse WOMAC dimension scores in patients who were obese included the number of comorbidities, an infrapatellar index percentile less than 75, IOD Grade 2, and the number of complications after discharge.

For patients with knee osteoarthritis who were severe or morbidly obese, various lower limb anthropometric features, degree of IOD, and postoperative complications negatively influenced postoperative WOMAC scores.

Level II Prognostic Study. See Guidelines for a complete description of levels of evidence.