Background: The International Knee Documentation Committee Subjective Knee Form (IKDC SKF) is a patient-reported knee-specific outcome measure that has been shown to be a reliable, valid, and responsive measure for patients with a variety of knee conditions. Further testing is required to compare the reliability and responsiveness of the IKDC SKF to other commonly used patient-reported outcome measures for patients with articular cartilage lesions.
Hypothesis: The IKDC SKF has equal or better levels of reliability and responsiveness than the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), modified Cincinnati Knee Rating System (CKRS), and the Short Form 36 in patients with articular cartilage lesions.
Study design: Cohort study (diagnosis); Level of evidence, 2.
Methods: Reliability was assessed by administering the 4 patient-reported outcome measures to 17 individuals who had undergone articular cartilage surgery 5 years before participation in this study. Responsiveness was determined by administering the 4 patient-reported outcome measures to 51 individuals with diagnosed focal articular cartilage defects who were scheduled to undergo surgical treatment. In both groups, the outcome measures were administered at baseline and at 6 and 12 months' follow-up. Participants also provided a global rating of change in comparison to baseline at the 6- and 12-month follow-ups.
Results: Test-retest reliability coefficients were 0.91 and 0.93 for the IKDC SKF at the 6- and 12-month follow-ups, respectively. The effect sizes and standardized response means were large (>0.80) at 6 months after surgery for the WOMAC pain, physical function, and total scores and 12 months after surgery for the IKDC SKF; WOMAC pain, physical function, and total; and CKRS scores. Six months after surgery, significant differences between those who were improved compared with those who were unchanged or worse were found only for the IKDC SKF. Twelve months after surgery, significant differences between the improved and unchanged groups were found for all of the knee-specific patient-reported outcome measures. Finally, the IKDC SKF, WOMAC, and CKRS scores were able to differentiate between individuals who perceived themselves to be improved versus not improved and the minimum clinically important difference for the IKDC SKF was 6.3 at 6 months and 16.7 at 12 months.
Conclusion: The reliability and responsiveness of the IKDC SKF is comparable with other commonly used patient-reported outcome measures for patients with articular cartilage lesions. The IKDC SKF is a suitable alternative to other commonly used knee-specific instruments for measuring symptoms, daily function, and level of symptom-free sports activity in patients undergoing articular cartilage surgery.