Fig. 2
The graphs (derived from the interaction models) illustrate the longitudinal changes in maximum JSN [range 0 to 3], cartilage T2 [in ms], and WOMAC pain score [range 0 to 20] over 4 years. The depression-BMI interactions were statistically significant with WOMAC pain (p < 0.001). The p-value for the depression-BMI interaction on JSN was p = 0.08; the interaction was not significant for cartilage T2 (p = 0.27). The figure illustrates that the compound effects of obesity and depression on OA are greater than their individual effects: in all three outcomes, the difference between the normal BMI groups (denoted by X) is less than the obese groups (denoted by O). Thus, the effect of depression is stronger in the obese groups than the normal weight groups