Effect of body mass index on functional outcome in primary total knee arthroplasty - a single institution analysis of 2180 primary total knee replacements

Table 1 World Health Organization body mass index classification

WHO BMI classification
Underweight	< 18.5
Normal range	18.5-25
Overweight	≥ 25
Obese	≥ 30
Class 1 obese	30-34.9
Class 2 obese	35-39.9
Class 3 obese	≥ 40

WTO: World Health Organization; BMI: Body mass index.