Measures of knee function: International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, Knee Injury and Osteoarthritis Outcome Score (KOOS), Knee Injury and Osteoarthritis Outcome Score Physical Function Short Form (KOOS‐PS), Knee Outcome Survey Activities of Daily Living Scale (KOS‐ADL), Lysholm Knee Scoring Scale, Oxford Knee Score (OKS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Activity Rating Scale (ARS), and Tegner Activity Score (TAS)

Abstract

Patient-reported measures of knee function are important for the comprehensive assessment of rheumatology conditions in both clinical and research contexts. To merit inclusion in this review, measures of knee function were required to be patient reported and assess aspects considered important by adult patients with knee problems such as injury or osteoarthritis (OA). Therefore, measures used in rheumatology, orthopedics, and sports medicine were considered. Dimensions deemed to be important to patients included pain, function, quality of life, and activity level. To identify instruments fulfilling these criteria, we utilized published reviews of knee instruments (1), knee OA instruments (2), and measures for use in patellofemoral arthroplasty (3). Based on these reviews, as well as extensive searches of more recent literature, we included the following 9 patient-reported outcomes: Activity Rating Scale, International Knee Documentation Committee Subjective Knee Evaluation Form, Knee Injury and Osteoarthritis Outcome Score, Knee Injury and Osteoarthritis Outcome Score Physical Function Short Form, Knee Outcome Survey Activities of Daily Living Scale, Lysholm Knee Scoring Scale, Tegner Activity Scale, Oxford Knee Score, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Although the WOMAC can be applied to the hip and knee, this study contains data only applicable to the knee. Measures assessing activity level are listed separately. Psychometric data pertaining to the reliability and responsiveness of each patient-reported outcome are shown in Tables 1 and ​and2.2. The number of psychometric reports concerning each instrument ranges from 2–27. A higher number of reports indicates a higher degree of certainty in interpretation of the psychometric properties. Table 1 Summary of reliability data* Table 2 Summary of responsiveness data* Psychometric properties were based on data provided in Tables 1 and 2, and interpreted using standardized guidelines. Internal consistency was considered adequate if Cronbach’s alpha was at least 0.7 (4), and test–retest (intra-rater) reliability was adequate if the intraclass correlation coefficient was at least 0.8 for groups and 0.9 for individuals (5). Floor and ceiling effects were considered to be absent if no participants scored the bottom or top score, respectively, and acceptable if 0.8 were considered large (9). In this context, the minimum clinically important difference is the amount of change of a patient-reported outcome that represents a meaningful change to the patient, while the patient-acceptable symptom state is the least abnormal function score at which patients would consider themselves having acceptable function (10).