The structural validity of the IKDC and its relationship with quality of life following ACL reconstruction

Objective: The purpose of this study was to (a) examine the structural validity of the International Knee Documentation Committee Subjective Knee Form in light of previously reported dimensionality issues, and (b) examine the relationships between the IKDC and patients’ knee-related quality of life 2-9 years after anterior cruciate ligament (ACL) reconstruction. Methods: A prospective research design was employed, wherein 319 patients (mean age = 29.07, SD = 9.03) completed the IKDC before surgery, 191 patients (mean age = 29.71, SD = 9.36) completed the IKDC at 6 months post-surgery, and 132 patients (mean age = 34.34, SD = 7.89) completed the IKDC and the Anterior Cruciate Ligament Quality of Life Survey (ACL-QOL) at 2-9 years post-surgery. Results: Bayesian structural equation modeling analysis confirmed the two-factor structure (symptom & knee articulation and activity level) represented the most accurate conceptualization of perceived knee function across the three time-points. Moreover, findings revealed that of the two IKDC subscales pre-operatively, activity level was most strongly associated with long-term quality of life at 2-9 years following surgery, whereas 2-9 years post-operatively, symptoms and knee articulation was most strongly associated with long-term quality of life. Conclusions: The IKDC provides clinicians with a convenient total score to assess patients’ perceived knee function, but its unidimensional factor structure is a poor representation of its items and fails to detect discrepancies in patients’ post-operative quality of life, such as the relative importance of perceived knee activity level before reconstructive surgery.