Table 4

Mediation effects for outcome WOMAC pain over 36 months: association of change in cartilage thickness loss over 24 months, with change in WOMAC knee

Mediator: synovitis score change over 24 months
Mean change in WOMAC knee pain over 36 months
Mediator: BML score change over 24 months
Mean change in WOMAC knee pain over 36 months
Exposure: 0.1 mm cartilage thickness loss over 24 months
 Controlled direct effect0.16 (−1.80 to 2.12)0.24 (−1.73 to 2.19)
 Indirect effect0.04 (−1.92 to 2.00)−0.003 (−1.96 to 1.96)
 Total effect0.16 (−1.77 to 2.15)0.23 (−1.73 to 2.19)
 Proportion
 mediated
19.78% (−1.65% to 41.21%)Proportion too small to calculate—not a mediator
Exposure: 0.05 mm cartilage thickness loss over 24 months
 Controlled direct effect0.08 (−1.88 to 2.04)0.12 (−1.84 to 2.08)
 Indirect effect0.02 (−1.94 to 1.98)−0.002(−1.96 to 1.96)
 Total effect0.10 (−1.86 to 2.06)0.12 (−1.84 to 2.08)
 Proportion
 mediated
19.78% (−1.65% to 41.21%)Proportion too small to calculate—not a mediator
  • All models adjusted for age, sex, BMI, race and depressive symptoms (CESD).

  • Positive(+) coefficient indicates an increase in the outcome WOMAC pain.

  • Models for mediation by change in synovitis score adjusted for standard covariates above +baseline BML score.

  • Models for mediation by change in BML score adjusted for standard covariates above +baseline synovitis score.

  • BMI, body mass index; BML, bone marrow lesion; CESD, Center for Epidemiologic Studies Depression Scale; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index.