Rationale for a Parsimonious Measure of Subjective Knee Function Among Individuals With Anterior Cruciate Ligament...

Area of Science:

• Orthopedics
• Sports Medicine
• Rehabilitation Science

Background:

• The International Knee Documentation Committee Subjective Knee Evaluation Form (IKDC) is widely used for assessing knee function post-anterior cruciate ligament reconstruction (ACLR).
• Traditional validation methods have limitations in confirming if the IKDC accurately measures knee function as intended.
• Rasch analysis offers a more robust approach to validate patient-reported outcome measures like the IKDC.

Purpose of the Study:

• To evaluate the psychometric properties of the IKDC and a newly proposed reduced-item instrument.
• To assess the instruments' ability to classify health status in individuals with ACLR.
• To examine the relationships between subjective knee function and objective measures of strength and performance.

Main Methods:

• A cross-sectional laboratory study involving 77 individuals with primary unilateral ACLR and 76 age-matched controls.
• Rasch analysis was employed to assess the psychometric properties of the IKDC.
• Receiver operator characteristic curves and correlation analyses were used to evaluate diagnostic accuracy and relationships with objective measures.

Main Results:

• Rasch analysis facilitated the development of an 8-item IKDC instrument (IKDC-8) with improved psychometric properties and precision.
• Both the IKDC and IKDC-8 demonstrated excellent ability to classify participants with ACLR versus controls.
• No significant differences were found in the diagnostic accuracy or the associations between subjective and objective knee function measures.

Conclusions:

• The IKDC-8 provides a reliable and valid, yet more concise, measure of subjective knee function.
• This reduced instrument enhances score interpretability and clinical utility by shortening administration time.
• The IKDC-8 effectively measures a single construct of knee function without compromising diagnostic capability or its relationship with objective recovery measures.