Controlling for confounders
The addition of age, sex, change in pain, and radiographic severity (K & L grade) as predictors in the models, with activity limitations at t1 as the dependent variable and activity limitations at t0 and change in muscle strength as independent variables, did not affect the strength of the association between change in muscle strength and performance-based activity limitations by more than 10%. The strength of the association between change in muscle strength and self-reported activity limitations decreased by 13.5%. A positive association was found between change in pain and change in activity limitations measured with the WOMAC-pf, walk test, and stair-climb test (see table 2, model 4)