Table 3.

Trajectory relative risk ratiosa

Baseline characteristic/factor RR (95% CI)Pain trajectory groups
C (moderate regression)E (major regression)B (severe progression)D (moderate progression)F (constant severe)
n = 207n = 23n = 35n = 180n = 74
BMI1.06 (1.00 to 1.13)0.96 (0.85 to 1.10)1.07 (0.96 to 1.19)1.09 (1.02 to 1.16)b1.10 (1.01 to 1.20)b
Highest achieved education level
  Primary or secondary schoolrefrefrefrefref
University/college0.53 (0.32 to 0.87)b0.83 (0.27 to 2.51)0.33 (0.16 to 0.95)b0.44 (0.24 to 0.80)b0.55 (0.23 to1.31)
>1 comorbidity1.75 (1.10 to 2.77)b1.37 (0.48 to 3.85)2.87 (1.23 to 6.67)b1.23 (0.74 to 2.08)2.65 (1.25 to 6.99)b
WOMAC physical function subscalec1.04 (1.02 to 1.06)b1.13 (1.09 to 1.17)b1.01 (0.98 to 1.05)1.09 (1.07 to 1.12)b1.14 (1.11 to 1.18)b
Knee joint space tenderness1.70 (1.07 to 2.69)b2.13 (0.76 to 6.02)2.84 (1.21 to 6.67)b3.86 (2.28 to 6.62)b2.03 (0.96 to 4.33)
Painful flexion knee0.91 (0.56 to 1.49)0.14 (0.03 to 0.69)b0.90 (0.37 to 2.19)0.77 (0.44 to 1.33)1.08 (0.51 to 2.29)
  • a Relative to reference trajectory (constant mild, group A), n = 186.

  • b P<0.05.

  • c RR per unit increase. A higher WOMAC score indicates more limitations due to physical health. BMI = body mass index. RR = relative risk ratio (obtained by multinomial logistic regression, adjusted for age and sex. Nagelkerke R2 = 0.42 for the model). WOMAC = Western Ontario and McMaster Universities Osteoarthritis Index.