Internal construct validity of the Oxford Knee Scale: Evidence from Rasch measurement

Abstract

Data from the OKS were consistent with the expectations of the unrestricted (partial credit) derivation of the Rasch model. The targeting of the instrument shows good coverage of thresholds across the whole construct and has good reliability (internal consistency) with a high patient separation. Consequently, this scale can be used in confidence with the knowledge that it is a unidimensional scale largely free of bias.