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.

Table 2 Pre- and post-operative functional outcome scores

	Group 1 (BMI < 25)	Group 2 (BMI > 25)
WOMAC scores
Pre-operative	52.7 (1-84)	53.7 (3-96)	P = 0.5
6 mo post-operative	29.7 (1-83)	27 (1-95)	P = 0.075
SF-36 Scores
Pre-operative	48.8 (10.4-90.6)	48.25 (3.3-94.6)	P = 0.83
6 mo post-operative	61.34 (1-83)	62.15 (7.3-99.4)	P = 0.7

WOMAC: Western Ontario and McMaster University Arthritis Index; BMI: Body mass index.

Table 3 Sub-group analysis of post-operative functional outcome scores

	BMI < 25	BMI 25-29	BMI 30-34	BMI 35-39	BMI > 40
	Normal	Overweight	Class 1 obese	Class 2 obese	Class 3 obese
WOMAC scores
6 mo post-operative	29.67	25.8	25.5	30.8	28.6
SF-36 Scores
6 mo post-operative	61.34	63.93	63.65	58.16	58.47

WOMAC: Western Ontario and McMaster University Arthritis Index; BMI: Body mass index.