Table 2 Uni- and multivariable linear regression analyses of the dichotomized percentage of non-contractile muscle tissue in the vastus medialis muscle on muscle strength of the knee extensors (normalized to body weight) and GUG time in patients with knee osteoarthritis. The multivariable analyses show the adjusted associations including the different possible confounders sex, age, BMI and radiographic severity

Unadjusted association, uni-variable analysis:

Non-contractile tissue

-0.25

0.006^a

-0.43 – -0.08

1.09

0.021^a

0.17 – 2.01

Adjusted association, multivariable analysis including the four possible confounders: sex, age, BMI and radiographic severity:

Non-contractile tissue

-0.15

0.049^a

-0.30 – 0.00

0.50

0.248

-0.35 – 1.34

 Sex

-0.52

 < 0.001^a

-0.67 – -0.36

1.09

0.017^a

0.20 – 1.98

 Age

-0.01

0.176

-0.02 – 0.00

0.07

0.022^a

0.01 – 0.13

 BMI

-0.02

0.005^a

-0.04 – -0.01

0.20

 < 0.001^a

0.11 – 0.29

 Radiographic severity

0.02

0.836

-0.14 – 0.17

0.41

0.364

-0.48 – 1.30

Adjusted association, multivariable analysis per confounder, to assess the effect on B:

Non-contractile tissue

-0.20

0.009^a

-0.35 – -0.05

0.98

0.035^a

0.07 – 1.90

 Sex

-0.51

 < 0.001^a

-0.67—-0.05

1.00

0.047^a

0.01 – 1.99

Non-contractile tissue

-0.25

0.006^a

-0.43 – -0.08

1.09

0.021^a

0.17 – 2.00

 Age

0.00

0.524

-0.02 – 0.01

0.05

0.115

-0.01 – 0.12

Non-contractile tissue

-0.21

0.025^a

-0.39 – -0.03

0.67

0.130

-0.20 – 1.55

 BMI

-0.02

0.031^a

-0.04 – 0.00

0.19

 < 0.001^a

0.10 – 0.29

Non-contractile tissue

-0.26

0.006^a

-0.44 – -0.08

1.03

0.029^a

0.11 – 1.96

 Radiographic severity

0.02

0.813

-0.17 – 0.21

0.67

0.183

-0.32 – 1.66