Does body mass index influence improvement in patient reported outcomes following total knee arthroplasty? A retrospective analysis of 3918 cases

Table 4 Preoperative, postoperative, and pre/post-change (Δ) PROMIS scores stratified by BMI classification

BMI	18.5–25 kg/m²	25.01–30 kg/m²	30.01–40 kg/m²	> 40 kg/m²	P-value
PROMIS—pain intensity	n = 231	n = 621	n = 986	n = 244
Preoperative	52.4 ± 7.2	53.1 ± 7.2	54.6 ± 7.6	55.7 ± 7.3	< 0.001
Postoperative	46.7 ± 8.7	47.0 ± 8.4	47.9 ± 8.9	47.8 ± 8.7	0.061
Δ	− 5.7 ± 9.5	− 6.1 ± 9.3	− 6.7 ± 10.2	− 7.9 ± 9.9	0.059
PROMIS—pain interference	n = 244	n = 655	n = 1048	n = 256
Preoperative	62.3 ± 6.9	63.3 ± 6.9	65.2 ± 7.1	65.7 ± 6.4	< 0.001
Postoperative	56.8 ± 8.9	57.3 ± 8.6	58.6 ± 9.0	58.8 ± 9.3	0.002
Δ	− 5.5 ± 9.5	− 6.0 ± 8.9	− 6.6 ± 9.4	− 6.9 ± 8.9	0.220
PROMIS—physical function	n = 69	n = 207	n = 311	n = 77
Preoperative	37.9 ± 7.6	36.3 ± 7.1	35.6 ± 6.7	34.5 ± 6.8	0.017
Postoperative	40.6 ± 8.5	40.1 ± 7.7	39.9 ± 8.1	39.1 ± 7.5	0.697
Δ	2.7 ± 8.7	3.7 ± 7.5	4.3 ± 8.0	4.6 ± 7.4	0.378
PROMIS—mobility	n = 149	n = 381	n = 611	n = 146
Preoperative	36.6 ± 4.9	36.9 ± 4.7	35.3 ± 4.8	34.6 ± 4.1	< 0.001
Postoperative	39.8 ± 6.7	40.7 ± 6.3	39.0 ± 6.1	38.3 ± 5.6	< 0.001
Δ	3.2 ± 6.3	3.8 ± 6.2	3.7 ± 6.1	3.7 ± 6.2	0.784
PROMIS—mental health	n = 179	n = 506	n = 777	n = 206
Preoperative	49.2 ± 9.2	49.5 ± 8.6	48.1 ± 9.2	46.8 ± 9.7	0.002
Postoperative	49.7 ± 9.1	49.8 ± 8.7	49.3 ± 9.2	48.3 ± 9.6	0.247
Δ	0.49 ± 7.0	0.36 ± 7.3	1.2 ± 7.6	1.5 ± 7.6	0.122
PROMIS—physical health	n = 191	n = 519	n = 830	n = 212
Preoperative	42.3 ± 7.5	41.0 ± 6.7	39.1 ± 6.9	37.1 ± 6.8	< 0.001
Postoperative	44.9 ± 8.2	44.6 ± 7.4	43.0 ± 7.8	42.3 ± 7.5	< 0.001
Δ	2.6 ± 7.9	3.5 ± 7.4	3.8 ± 7.5	5.2 ± 7.3	0.003

Bold indicates statistical significance
BMI body mass index, PROMIS Patient-Reported Outcome Measurement Information System

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