Construct validity of the Moroccan KOOS via SF-36 correlations in patients with knee disorders

Background: The knee injury and osteoarthritis outcome score (KOOS) is a widely used patient-reported measure of knee pain, symptoms, function, and quality of life (QoL). This study aimed to evaluate the construct validity of the Moroccan KOOS by examining its convergent and divergent validity with SF-36 dimensions. Methods: A cross-sectional study was conducted including patients with knee disorders in Morocco. Participants completed the Moroccan version of the KOOS and the SF-36 health-related QoL questionnaire. Construct validity was evaluated by examining correlations between the five KOOS subscales (Pain, Symptoms, Activities of Daily Living (ADL), Sport/Rec, and QoL) and the eight SF-36 dimensions. Results: Strong positive correlations were observed between KOOS subscales and SF-36 Physical Functioning (D1) and Role Physical (D2), particularly for Pain, ADL, Sport/Rec, and QoL (r=0.405 – 0.769, p<0.01), supporting convergent validity. Significant positive correlations were found between KOOS subscales and SF-36 Bodily Pain (D3) (r=0.283 to 0.698, p<0.01). Positive correlations were also observed with Vitality (D5) and Role Emotional (D7), whereas weak or non-significant correlations with General Health (D4) and Social Functioning (D6) supported divergent validity. Additionally, negative correlations with Mental Health (D8) were observed for most KOOS subscales, further confirming construct distinctiveness. Conclusions: The Moroccan version of the KOOS demonstrated very good construct validity, consistent with findings from other cross-cultural validations, confirming its relevance and robustness in the Moroccan population with knee disorders.