J Korean Orthop Assoc.  2022 Jun;57(3):233-239. 10.4055/jkoa.2022.57.3.233.

Changes in the Body Mass Index after Total Knee Arthroplasty in Asians

• Choi Wk
• Nam JH
• Jun CM
• Choi SC

• KMID: 2530669
• DOI: http://doi.org/10.4055/jkoa.2022.57.3.233

Abstract

Purpose
This study examined the changes in the body mass index (BMI) and the effects of BMI on the knee function and risk factors for an increase in BMI after total knee arthroplasty (TKA) in Asians.
Materials and Methods
A prospective observational study was conducted on 100 cases of TKA performed by one surgeon. Obesity was defined as BMI ≥25 kg/m 2 . The BMI and Knee Society Score, consisting of the Knee Score and Function Score, were measured on the day before surgery and one year after surgery.
Results
The BMI decreased or was maintained in 34 cases (34%) and increased in 66 cases (66%) one year after surgery. An increase in BMI of 5% or more was considered a clinically significant increase in BMI and occurred in 28 cases (28%). The patients with an increased BMI by more than 5% showed a significantly lower knee function score. The age and preoperative function score were significantly associated with an increased BMI by more than 5%. As the age increased by one year, the odds ratio at which the BMI would increase by more than 5% one year after surgery was 0.905. Moreover, as the preoperative function score increased by one point, the odds ratio that the BMI would increase by 5% one year after surgery was 0.902. In other words, a younger preoperative age and a lower preoperative function score mean a higher risk of a more than 5% postoperative increase in BMI.
Conclusion
The BMI increased by more than 5% one year after surgery in 28% of the TKA patients examined. They had a lower functional score. The risk factors for a more than 5% increase in BMI after TKA were young age and a low preoperative function score. Therefore, surgeons should educate patients, particularly those who are young or have a low preoperative function score, so that the patient’s BMI would not increase after surgery.

Keyword

obesity; body mass index; total knee arthroplasty; Knee Society Score