Table 4.

Interaction effects of obesity and reproductive and hormone factors on knee pain and clinical KOA

Variables	Knee pain			Clinical KOA
	OR (95% CI)	Multiplicative interaction, p-value	Additive interaction, AP	OR (95% CI)	Multiplicative interaction, p-value	Additive interaction, AP
BMI + pregnancy		0.570	0.08(0.07, 0.22)*		0.946	−0.02(−0.31, 0.27)
BMI (−) pregnancy (< 3)	1			1
BMI (−) pregnancy (≥3)	1.16(1.01–1.33)*			1.00(0.76–1.33)
BMI (+) pregnancy (< 3)	1.48(1.27–1.73)*			1.65(1.24–2.21)*
BMI (+) pregnancy (≥3)	1.78(1.55–2.04)*			1.63(1.26–2.12)*
BMI + abortion		0.544	0.07(−0.08, 0.23)		0.288	−0.14(− 0.42, 0.15)
BMI (−) abortion (−)	1			1
BMI (−) abortion (+)	1.06(0.92–1.23)			1.20(0.90–1.60)
BMI (+) abortion (−)	1.48(1.25–1.74)*			1.90(1.42–2.55)*
BMI (+) abortion (+)	1.66(1.44–1.92)*			1.85(1.40–2.42)*
BMI + menopause		0.329	0.18(−0.05, 0.41)		0.298	−0.15(− 0.67, 0.38)
BMI (−) menopause (−)	1			1
BMI (−) menopause (+)	1.20(0.93–1.54)			2.08(0.96–4.51)
BMI (+) menopause (−)	1.32(0.94–1.85)			2.73(1.09–6.88)*
BMI (+) menopause (+)	1.84(1.43–2.38)*			3.32(1.53–7.20)*
BMI + HT		0.828	0.09(−0.33, 0.51)		0.916	0.20(− 0.33, 0.74)
BMI (−) HT (−)	1			1
BMI (−) HT (+)	1.62(1.14–2.32)*			1.72(0.93–3.17)
BMI (+) HT (−)	1.52(1.39–1.67)*			1.62(1.37–1.93)*
BMI (+) HT (+)	2.36(1.62–3.44)*			2.95(1.77–4.92)*
BMI + contraceptives use		0.019*	0.26(0.11–0.42)*		0.133	−0.16(−0.54, 0.22)
BMI (−) contraceptives (−)	1			1
BMI (−) contraceptives (+)	1.03(0.87–1.22)			1.52(1.12–2.06)*
BMI (+) contraceptives (−)	1.44(1.30–1.59)*			1.74(1.44–2.11)*
BMI (+) contraceptives (+)	2.00(1.68–2.38)*			1.96(1.46–2.62)*

AP attributable proportion of interaction, HT, post-menopausal hormone replacement therapy, BMI (+) ≥24.0 kg/m², BMI (−) < 24.0 kg/m², Adjusted for age (continuous), education level, alcohol consumption, physical exercise, work posture, and shift work. *p-value < 0.05