Effect of obesity on pain and functional recovery following total knee arthroplasty

Knee osteoarthritis is prevalent, disabling joint disease that affects almost 4% of the global population. Literature suggested that obesity is the major risk factor for the progress of OA, but there is limited data available on the impact of the degree of obesity on patient-reported outcomes following this procedure. Therefore in this research, the authors found that participants across all BMI groups achieved similar results concerning self-reported pain, function, and satisfaction at 24 months following total knee arthroplasty.

Obesity can be a risk factor for health issues following total knee arthroplasty, however, data regarding this is insufficient. The study aimed to evaluate the degree to which the obesity levels influence the recovery process along with patient-reported pain, satisfaction, and function with surgery following total knee arthroplasty.

The patients with ≥40 years of age and primary osteoarthritis. Who went through total knee arthroplasty at 1 of 4 medical centres were selected for the analysis and classified into five categories as per the WHO classification of BMI. The assessment of the relationship between BMI and function and pain were done over the time intervals of 0 to 3, 3 to 6 months, and six months to 2 years using a piecewise linear model. The relationship between BMI group and patient-reported outcomes at two years were also assessed. Multivariable models adjusted for race, sex, age, musculoskeletal functional limitations index, study site, diabetes, and pain medication use.

Nineteen percent of patients exhibited BMI of <25 kg/m (normal weight), 32% showed BMI of 25 to 29.9 kg/m (overweight), 27% exhibited BMI of 30 to 34.9 kg/m (class-I obese), 12% showed BMI of 35 to 39.9 kg/m (class-II obese), and 9% showed BMI of ≥40 kg/m (class-III obese). Worse preoperative WOMAC pain and function scores and higher improvement from baseline to 3 months was noticed among the patients with higher BMI. The average change in function and pain from 3 to 6 months and from 6 months to 2 years was equal overall BMI groups. Participants in all BMI groups had similar levels of function, pain, and satisfaction at 2 years

Participants in the greater BMI groups were able to obtain perfect function and pain scores equivalent to those in the non-obese and class-I obese groups, due to the distinctive trajectory of recovery in the first three months after the total knee arthroplasty. These findings can aid surgeons to explore assumptions of pain relief and functional improvement with total knee arthroplasty candidates with greater BMI.