Reliability, validity and responsiveness of the Portuguese version of the Knee injury and Osteoarthritis Outcome Score – Physical Function Short-form (KOOS-PS)

Summary 

Objective

To test the reliability, validity and responsiveness of the Portuguese version of the Knee injury and Osteoarthritis Outcome Score – Physical Function Short-form (KOOS-PS).

Methods

The Portuguese full KOOS and Medical Outcomes Study – 36 item Short-Form (SF-36) questionnaires, and a form of individual characteristics of the patients were applied to 85 subjects with knee osteoarthritis (OA).

Results

Cronbach's alpha coefficient was 0.89 and intraclass correlation coefficient (ICC) was 0.85, certifying that KOOS-PS reliability was acceptable. Construct validity was supported by the confirmation of the five predefined hypotheses involving expected correlations between KOOS-PS scale, KOOS subscales and SF-36 subscales. An additional predefined hypothesis was also confirmed with the subjects that need walking aids obtaining higher KOOS-PS scale scores (P=0.011). Responsiveness to 4 weeks of conventional physical therapy treatments and to a 6-week health education and exercise program was demonstrated with a standardized effect size of 0.88 and 0.50, and a standardized response mean of 1.21 and 0.73, respectively.

Conclusion

The Portuguese KOOS-PS evidenced acceptable psychometric characteristics.

Key words: Knee, Osteoarthritis, Functional status, KOOS-PS