Table 6. Baseline and change in isometric extension and flexion strength in knees contralateral and ipsilateral to THA.

Adjusted mean baseline isometric values and change over 4 years ± standard error of the mean (SEM) (Newtons) for isometric strength by THA status. Contralateral vs ipsilateral knee comparisons are paired, within subject differences. Contralateral and ipsilateral comparisons to right knees of subjects with No THA and adjusted mean values are from multivariate linear regression models.

Maximum isometric Strength (Newtons) BASELINE:	Unilateral THA		No THA (Controls) right knee	Contralateral vs ipsilateral		Contralateral vs control
	Contralateral knee	Ipsilateral knee		P-value (paired t-test) #	Paired difference (95% CI) #	P-value ##	Adj mean difference (95% CI) ##
Extension	334.1±26.1	327.0±25.9	340.9±26.1	0.64	−7.1 (−37.3; 23.2)	0.90	−3.6 (−65.7; 33.7)
Flexion	137.7±15.6	138.1±15.5	131.6±15.6	0.94	0.4 (−9.7; 10.5)	0.72	−0.6 (−39.3; 27.2)
CHANGE: BASELINE TO 4 YEARS
Extension	−51.6±21.9	−15.5±22.4	−4.1±21.8	0.04	−42.0 (−2.8; −81.1)	0.009	−73-3 (−127.4; −19.3)
Flexion	−33.9±16.1	−44.7±16.3	−58.7±16.0	0.52	−11.3 (−46.8; 24.2)	0.12	30.1 (−67.8; 7.6)

^#paired difference = contralateral – ipsilateral; P-value and 95% from paired t-test

^##P-value and adjusted mean difference and 95% CI from the multivariate regression model, contralateral vs control knees. Covariates were OA risk factors including: self-reported history of knee injury or surgery, familial predisposition of OA, defined as a total knee replacement for OA in a biological parent or sibling, Heberden’s nodes, age, gender BMI and PASE score.