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Table 3 Baseline characteristics and predictors of unilateral versus bilateral knee replacement, univariate and multivariate analyses

From: Risk factors for joint replacement in knee osteoarthritis; a 15-year follow-up study

  Total Knee replacement Unadjusted Adjusteda
Variable (n = 66) Unilateral (n = 29) Bilateral (n = 37) OR (95% CI) p value OR (95% CI) p value
Female, % (no.) 68% (45) 76% (22) 62% (23) 1.0 (0.9 – 1.0) 0.24   
Age (years), mean (SD) 61.3 (10.0) 62.9 (11.0) 59.9 (9.0) 0.5 (0.2 – 1.5) 0.23   
BMI, grade, mean (SD) 2.2 (0.9) 1.9 (0.9) 2.5 (0.9) 2.3 (1.2 – 4.3) 0.009   
WOMAC, mean (SD), baseline:
- Pain 196 (95) 206 (91) 189 (98) 1.0 (1.0 – 1.0) 0.48 1.0 (1.0 – 1.0) 0.42
- Stiffness 87(46) 83 (47) 91 (44) 1.0 (1.0 – 1.0) 0.44 1.0 (1.0 – 1.0) 0.76
- Function 692 (332) 682 (320) 701 (340) 1.0 (1.0 – 1.0) 0.82 1.0 (1.0 – 1.0) 0.69
- Total 976 (446) 970 (420) 981 (465) 1.0 (1.0 – 1.0) 0.92 1.0 (1.0 – 1.0) 0.66
JSN grade, mean (SD) 2.0 (0.9) 1.9 (0.9) 2.1 (0.9) 1.3 (0.8 – 2.3) 0.30 2.2 (1.0 – 4.6) 0.05
Radiological sum score, mean (SD) 5.8 (2.3) 5.4 (2.4) 6.1 (2.2) 1.1 (0.9 – 1.4) 0.26 1.4 (1.0 – 1.9) 0.05
BML grade, mean (SD)b, c 2.4 (1.6) 2.5 (1.7) 2.4 (1.5) 1.0 (0.7 – 1.3) 0.82 0.9 (0.6 – 1.3) 0.63
Synovitis grade, mean (SD)b, d 2.9 (0.9) 2.8 (1.1) 2.9 (0.7) 1.2 (0.7 – 2.1) 0.61 1.1 (0.6 – 2.1) 0.78
Effusion grade, mean (SD)b, e 2.7 (1.6) 2.4 (1.7) 3.0 (1.5) 1.3 (0.9 – 1.8) 0.20 1.2 (0.8 – 1.7) 0.39
  1. OR odds ratio, CI confidence interval, No. number, SD standard deviation, BMI body mass index, WOMAC Western Ontario and McMaster Universities OA index, JSN joint space narrowing, BML bone marrow lesion
  2. aAdjusted for sex, age and BMI; b Based on 56 participants with total knee arthroplasty, accessible MRI scan and tibiofemoral osteoarthritis; c Ordered into a ten point ordinal scale (Grade 1 = 0 - 10% BML, grade 2 = >10 - 20% BML etc.); d Ordered into a five point ordinal scale (Grade 1 = 0 - <5; grade 2 = 5 - <10 etc.); e Ordered into an eight point ordinal scale (Grade 1 = 0 - <5; grade 2 = 5 - <10 etc.) (maximum effusion score = 38)