The Patient-Reported Outcomes Measurement Information System (PROMIS)-Plus-Osteoarthritis of the Knee (OAK) profile integrates universal PROMIS items with knee-specific items across 13 domains. We evaluated the psychometric properties of a subset of six domains associated with quality of life in people with OAK.
In a cross-sectional study of OAK patients (n=600), we estimated reliability using Pearson and Spearman correlations with Knee Injury and Osteoarthritis Outcome Score (KOOS) subscores and known-groups validity with PROMIS Global Health. Measure responsiveness was tested via paired t-tests in a longitudinal study (n=238), pre/post total knee replacement.
Across the six domains, internal consistency reliability (Cronbach's alpha) was 0.77-0.95 and test-retest reliability (intraclass correlation coefficients) was ≥0.90. Correlations with Knee Injury and Osteoarthritis Outcome Score (KOOS) subscores and PROMIS Global supported convergent and divergent validity. Known-groups validity testing revealed better scores in all domains for high vs. low global status groups, and knee-specific items added value in physical function and pain. All domains reflected (p<0.001) better health status scores at follow up.
The six PROMIS-Plus-OAK profile domains demonstrated good psychometric characteristics. The measure integrates universal and knee-specific content to provide enhanced relevance, measurement precision and efficient administration for patient care and clinical research.