Table 4.

Mediation analysis: psychological variables as mediators

Outcome Variable	Direct Effect (c′)	Indirect Effect (a*b)	Total Effect (c)	95% CI for Indirect Effect	p-value (Indirect Effect)	R² (Model)
NPRS (Pain Score)	-0.18	-0.09	-0.27	-0.16 to -0.03	0.002	0.21
KOOS-PS (Physical Function)	1.23	0.67	1.90	0.28 to 1.05	0.004	0.18
EQ-5D-5 L (Quality of Life)	0.03	0.01	0.04	0.00 to 0.02	0.038	0.24

tDCS = Transcranial Direct Current Stimulation; NPRS = Numeric Pain Rating Scale; KOOS-PS = Knee Injury and Osteoarthritis Outcome Score– Physical Function Shortform; EQ-5D-5 L = EuroQol 5-Dimensions 5-Levels; PCS = Pain Catastrophizing Scale; CI = Confidence Interval; R² = Coefficient of Determination