Rationale for a Parsimonious Measure of Subjective Knee Function Among Individuals With Anterior Cruciate Ligament Reconstruction: A Rasch Analysis

Abstract

Context: The International Knee Documentation Committee (IKDC) Subjective Knee Evaluation is the most frequently used patient-reported measure of subjective knee function among individuals with ACL reconstruction (ACLR). Yet, limitations with traditional validation approaches leave it unclear whether the IKDC measures knee function as intended. Rasch analysis offers a robust validation approach, which may enhance clinical interpretation of the IKDC. Objective: 1) To assess the psychometric properties, 2) ability to classify health status, and 3) relationships between the IKDC and objective measures of strength and functional performance relative to a newly proposed reduced-item instrument. Design: Cross-sectional. Setting: Laboratory. Patients or other Participants: Seventy-seven individuals with primary, unilateral ACLR (21.9±7.8 years, 6.2±1.0 months post-surgery), and seventy-six age-matched controls. Main Outcome Measure(s): Rasch analysis was used to assess the psychometric properties of the IKDC. Receiver-operator-characteristic curves and logistic regression were used to assess the accuracy of classifying ACLR versus control participants. Correlations (Pearson and Spearman) were used to assess relationships between subjective knee function, quadriceps torque, and single-limb hop performance. Results: Rasch analysis aided the development of a reduced 8-item instrument (IKDC-8), which yielded improved psychometric properties in misfit analysis, percent of variance accounted for by one dimension (IKDC-8=71.5%; IKDC=56.7%), and item reliability. The IKDC was an outstanding diagnostic tool and the IKDC-8 was excellent, correctly classifying 87.2% and 82.7% of cases, respectively. The Hanley-McNeil formula found that there was no significant difference in the areas under the respective ROC curves. Equivalent associations between subjective and objective knee function were observed regardless of instrument used. Conclusions: We observed evidence of enhanced reliability and validity for a parsimonious measure of subjective knee function. The proposed instrument reduces the number of items, increases score interpretability as measuring a single construct, and improves the rating scale functioning, while not significantly diminishing its ability to classify ACLR versus control participants or changing existing relationships with objective measures of recovery. We suggest the IKDC-8 may enhance clinical use by reducing administration time, improving the interpretation of the subjective knee function score, and clarifying functional ability.

Evaluating Psychometric Properties of the International Knee Documentation Committee Subjective Knee Form in a Heterogeneous Sample of Post-Operative Patients

“…1,32,33,37 Further, multiple short form versions of the IKDC-SKF have been suggested in the literature, but initial efforts have primarily used small samples that do not well represent the patient population who completes the IKDC-SKF. 12,34 Therefore, assessment of the IKDC-SKF using recommended classical test theory procedures was warranted and the purpose of our study was to conduct EFA, CFA, and invariance testing procedures on the IKDC-SKF in a large, heterogenous sample of patients to assess the measurement properties of the scale or an alternate, psychometrically sound short form version of the scale. EFA resulted in a 9-item, 3-factor IKDC-SKF short form (IKDC-SKF-9; Appendix 1) supported by CFA and multi-group invariance testing; however, the proposed model did not meet all recommended measurement criteria and did not pass longitudinal invariance requirements.…”

“…The IKDC-SKF has been reported to have a unidimensional 32,37 and a multidimensional 1,8,33 factor structure with different items in the final models. Study methodology differences may contribute to the inconsistent findings as differences in samples (e.g., size, respondent population [e.g., healthy, 12 ACL injury, 1,34 ]) and analysis methodologies (e.g., EFA/CFA, 33 PCA, 32 Bayesian SEM, 1 Rasch, 12,34 factor and item retention criteria) exist between studies. For example, our study included a large, heterogenous sample of patients who had undergone arthroscopic knee surg-eries, while others have included smaller samples, healthy respondents, 12 or focused on different patient populations (e.g., ACL reconstruction, 1,34 meniscal lesions, 45 various patient pathologies 32,33.37 ).…”

“…8 The need for further item removal and the identification of a parsimonious short from was also supported with Rasch analysis; however, final model solutions differed with one retaining 5 items 12 and the other retaining 8 items. 34 Other concerns with these studies 12,34 are the use of small samples (i.e., 77 34 and 160, 12 respectively) and respondent pools (e.g., healthy respondents) who are not representative of the patient population with which the scale is used in clinical practice and research. Thus, further research is needed to make clearer recommendations on a parsimonious IKDC-SKF short form that can be used in practice and research.…”

Meniscal Allograft Transplants in Skeletally Immature Patients: A Systematic Review of Indications and Outcomes

“…To study and refine their measurement properties, the KOOS and IKDC have been investigated via Rasch Analysis. Conflicting findings were reported (see [37][38][39]). This is not surprising as Rasch Analysis is a strict model for testing the measurement requirements of patient-oriented outcome [40,41].…”

International Knee Documentation Committee Subjective Knee Form Latent Growth Model Analysis: Assessing Recovery Trajectories

“…Approximately 14 million Americans suffer from knee pathologies (e.g., osteoarthritis), which have profound health consequences (e.g., depression, cardiovascular disease, reduced quality of life) due to physical limitations. Patient Reported Outcome Measures (PROMs) have grown in importance in the last several decades [1,2] and are used to measure patients' perspectives on various biopsychosocial variables (e.g., knee health, depression) [3,4] and may provide critical information that may influence both empirical and clinical decision-making [5][6][7][8] over the course of medical treatment and recovery. Therefore, using PROMs to better understand how individuals recover from various knee pathologies is essential for evaluating patient-perceived healing and making clinical decisions postoperatively.…”