Table 3.

Multiple linear regression analysis on mental composite scale (MSC), stratified by self-reported bilateral knee pain and back pain (N = 780)

Predictor variable	Model #1 N = 780 β	SE	β	Model #2 N = 780 SE	β	Model #3 N = 780 SE
Intercept	54.6*	0.32	56.3*	4.60	51.8*	5.29
Four groups based on bilateral knee pain and back pain
1. No bilateral knee and no back pain	Reference		Reference		Reference
2. No bilateral knee pain and back pain	−1.92	1.07	−1.80	1.07	−1.91	1.06
3. Bilateral knee pain and no back pain	−1.76	1.17	−0.99	1.17	−1.20	1.17
4. Bilateral knee and back pain	−3.19**	1.07	−2.63**	1.08	−2.71**	1.09
R 2	0.011		0.037		0.041

Abbreviations: β, estimate; SE, standard error.

Model 1: unadjusted.

Model 2 included age, sex, race, education, and income.

Model 3 included Model 2 plus comorbidity and BMI.

^*p <.0001

^**p <.05.