Relationship of closed and open chain measures of strength with perceived physical function and mobility following unilateral total knee replacement

Background and Purpose: The association between closed-chain knee extensor strength and perceived physical function following primary knee replacement has not received much attention. The purpose of this investigation was to determine the relationship of closed and open chain measures of strength with self-reported measures of physical function and mobility following unilateral knee replacement. Methods: Subjects were 9 individuals (68. 7 ± 2.3 years) approximately 16 months postsurgery. The independent variables were closed-chain (elastic) and open-chain (isometric) measures of strength, while the dependent measures were perceived physical function (WOMAC) and mobility (Timed Up and Go, TUG). The relationship between independent and dependent variables was described using Spearman Rho correlation coefficients. Results: Force produced during the closed-chain assessment was strongly associated to the WOMAC physical function dimension (-.96) and total WOMAC score (-.87). A poor to low relationship existed between the open-chain measure of strength and the physical function dimension (-.34) and the total WOMAC score (-.17). Force production of the entire lower limb, measured in the closed-chain was moderately related (-.62) with the TUG. The association between knee extensor isometric torque and the TUG (-.25) was low. Conclusions: Closed-chain assessment of entire lower limb strength, rather than open-chain measures of knee extensor strength, may provide greater insight to functional limitations.