Limitations
ACL injury, ACL
The factor structure identified in this study may be sensitive to the study sample. We used the entire sample for our analyses in an effort to maintain power and precision, however we cannot be confident in the robustness of the analyses, especially given the alternative structures shown in previous work with other datasets. Only baseline, and not post-operative data was used for this analysis. Assessing additional time points and the measurement invariance of the proposed structure across time is beyond the scope of the initial CFA of the IKDC covered in this paper. Therefore, we cannot be sure that the bifactor model and essential unidimensionality shown here would have adequate fit in other datasets at later timepoints following ACL injury. Analyses of measurement invariance in other datasets from patients following an ACL injury would be required to assess consistency in the outcome measure’s dimensionality for this specific population. Our analysis represents one proposed structure for the IKDC which should be confirmed in other datasets first before investigating other psychometric properties which rely on the assumption of structural validity such as internal consistency reliability and cross-cultural validity.