Clinically meaningful thresholds for the Thai Kujala score in patellofemoral pain syndrome: Minimal clinically important improvement and patient acceptable symptom state.

INTRODUCTION/

OBJECTIVES

The Kujala score is a patient-reported outcome questionnaire used to evaluate symptoms and functional limitations in patellofemoral pain syndrome (PFPS). The Kujala score has been translated and adapted into many languages, including Thai; however, no studies have investigated the minimal clinically important improvement (MCII) and patient acceptable symptom state (PASS) for the Thai version of the Kujala score. This study aimed to evaluate the MCII and PASS of the Thai Kujala score and to identify factors associated with changes in Kujala scores.

METHODS

A prospective cohort study of 47 patients diagnosed with PFPS was conducted at Thammasat University Hospital. Patients completed the Kujala score, International Knee Documentation Committee score (IKDC) and Knee Injury and Osteoarthritis Outcome Score (KOOS) at baseline, 1 month, and 3 months. Anchor-based and distribution-based methods were used to calculate MCII and PASS. Regression analysis was performed to identify factors associated with changes in Kujala scores.

RESULTS

The MCII threshold for the Thai Kujala score was identified as ≥3.5 points, with an area under the curve (AUC) of 0.771 (95% confidence interval [CI]: 0.643-0.899, p = 0.002). The PASS threshold was a score of 72, with an AUC of 0.708 (95% CI: 0.561-0.855, Youden index = 0.310). The Kujala score demonstrated a strong correlation with the IKDC (Spearman's ρ = 0.701, p < 0.001) and a moderate correlation with the KOOS (Spearman's ρ = 0.401, p = 0.002). No demographic variables (age, sex, body mass index, or exercise status) were associated with changes in Kujala scores in multivariate analysis.

CONCLUSION

An improvement of ≥3.5 points in the Thai Kujala score reflects the MCII, while a score of 72 represents the PASS in patients with PFPS. Therefore, the Thai Kujala score shows strong correlation with the IKDC and the KOOS score. The Thai Kujala score can be used reliably as a patient-centered outcome measure in both clinical practice and research settings.

LEVEL OF EVIDENCE: Level II, diagnostic study.