Table 1.
Parameter estimates (95% confidence intervals) from multivariate linear mixed models with the following explanatory variables (one model per dependent variable) (i.e. average differences in outcome variables of knee pain and functioning between groups of categorical predictors and average change per single unit of continuous predictors).
| Parameter | WOMAC pain | WOMAC function | RAND-36 function | RAND-36 PCS (orthogonal) | RAND-36 MCS (orthogonal) | RAND-36 PCS (oblique) | RAND-36 MCS (oblique) |
|---|---|---|---|---|---|---|---|
| Age (divided by 10 years) | −3.81 (−9.02 to 1.40) | −3.88 (−9.67 to 1.91) | −0.95 (−4.29 to 2.40) | 1.21 (−1.25 to 3.68) | −0.68 (−3.78 to 2.41) | 0.62 (−2.06 to 3.30) | 0.22 (−2.56 to 3.00) |
| Gender (male vs. female) | −2.65 (−9.47 to 4.18) | −3.26 (−10.95 to 4.42) | 1.64 (−6.74 to 10.02) | 1.79 (−1.51 to 5.10) | −1.30 (−5.46 to 2.86) | 0.87 (−2.74 to 4.48) | −0.37 (−4.11 to 3.38) |
| Education (comprehensive school vs. upper secondary or vocational school) | 3.61 (−3.56 to 10.79) | 3.70 (−4.35 to 11.76) | −2.11 (−10.88 to 6.65) | −2.12 (−5.55 to 1.30) | −2.44 (−6.73 to 1.85) | −2.86 (−6.58 to 0.87) | −2.51 (−6.37 to 1.34) |
| Comorbidities (0−2 vs. ⩾3) | −7.81*a (−15.57 to −0.05) | −7.99 (−16.69 to 0.71) | 8.28 (−1.20 to 17.76) | 3.35 (−0.35 to 7.04) | 2.81 (−1.82 to 7.45) | 4.01*i (0.01 to 8.03) | 3.50 (−0.66 to 7.67) |
| Body mass index (<30.0 vs. ⩾30.0 kg/m2) | −3.28 (−9.69 to 3.14) | −4.30 (−11.52 to 2.94) | 7.24 (−0.67 to 15.15) | 3.16*f (0.08 to 6.24) | 1.54 (−2.33 to 5.42) | 3.25 (−0.11 to 6.62) | 2.63 (−0.86 to 6.13) |
| Employed vs. retired or unemployed | −2.17 (−12.06 to 7.72) | −10.55 (−21.49 to 0.38) | 2.58 (−9.36 to 14.52) | 1.43 (−3.20 to 6.05) | 0.27 (−5.54 to 6.08) | 1.12 (−3.92 to 6.17) | 1.45 (−3.78 to 6.68) |
| Marital status (cohabiting vs. living alone) | −1.87 (−9.19 to 5.44) | 1.11 (−7.13 to 9.34) | 3.30 (5.69 to 12.30) | 0.97 (−2.52 to 4.47) | −2.78 (−7.17 to 1.62) | −0.50 (−4.31 to 3.31) | −1.72 (−5.67 to 2.24) |
| Radiological grade (KL 2 vs. KL 3–4) | −5.07 (−11.36 to 1.23) | −5.03 (−12.11 to 2.04) | 11.66**d (3.93 to 19.38) | 3.64*g (0.63 to 6.65) | 2.95 (−0.84 to 6.74) | 4.11*g (0.82 to 7.40) | 3.67*j (0.26 to 7.09) |
| Duration of knee pain symptoms (<6 (median) vs. ⩾6 years) | −0.40 (−6.68 to 5.87) | 1.59 (−5.48 to 8.65) | −6.51 (−14.24 to 1.21) | −1.43 (−4.43 to 1.56) | −2.17 (−5.94 to 1.61) | −1.94 (−5.22 to 1.33) | −2.43 (−5.83 to 0.97) |
| Exercise (⩾2 times a week vs. ⩽1 times a week) | 0.32 (−6.29 to 6.92) | −5.46 (−12.88 to 1.97) | 11.03**e (2.93 to 19.13) | 2.16 (−1.00 to 5.31) | 1.46 (−2.51 to 5.43) | 2.07 (−1.38 to 5.51) | 2.42 (−1.15 to 6.00) |
| Group randomization (CBT intervention (n = 55) vs. control (n = 56)) | −3.57 (−10.15 to 3.01) | −0.60 (−8.00 to 6.80) | 1.03 (−7.05 to 9.10) | 0.23 (−2.92 to 3.38) | −1.18 (−5.15 to 2.78) | −0.25 (−3.69 to 3.19) | −0.64 (−4.21 to 2.93) |
| Time (baseline vs. follow-up average) | 18.42***b (14.50 to 22.34) | 13.25***c (9.45 to 17.05) | −0.95 (−4.29 to 2.40) | −2.07**h (−3.59 to −0.56) | 1.27 (−0.31 to 2.84) | −1.29 (−2.60 to 0.02) | 0.32 (−0.88 to 1.51) |
WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index (visual analogue scale (VAS) mm); RAND-36: Finnish-validated SF-36-item Health Survey; PCS: physical component summary; MCS: mental component summary; KL: Kellgren–Lawrence (KL) grade.
P ⩽ 0.05; **P ⩽ 0.01; ***P ⩽ 0.001.
7.81 lower pain score for those with 0−2 comorbidities. b18.42 higher pain score at baseline. c13.25 higher functional impairment at baseline. d11.66 better physical function for those with KL2 knee osteoarthritis. e11.03 better physical function for those exercising ⩾2 times a week. f3.16 higher PCS scores (orthogonal/oblique) for those with BMI <30.0 kg/m2. g3.64/4.11 higher PCS scores (orthogonal/oblique) for those with KL2 knee osteoarthritis. h2.07 lower PCS score (orthogonal) at baseline. i4.01 higher PCS scores (oblique) for those with 0−2 comorbidities. j3.67 higher MCS scores (oblique) for those with KL2 knee osteoarthritis.