The OARSI core set of performance-based measures for knee osteoarthritis is reliable but not valid and responsive

Abstract 

Purpose The Osteoarthritis Research Society International has identi ed a core set of performance-based tests of physi- cal function for use in people with knee osteoarthritis (OA). The core set consists of the 30-second chair stand test (30-s CST), 4 × 10 m fast-paced walk test (40 m FPWT) and a stair climb test. The aim of this study was to evaluate the reliabil- ity, validity and responsiveness of these performance-based measures to assess the ability to measure physical function in knee OA patients. 

Methods A prospective cohort study of 85 knee OA patients indicated for total knee arthroplasty (TKA) was per- formed. Construct validity and responsiveness were assessed by testing of prede ned hypotheses. A subgroup (n = 30) underwent test–retest measurements for reliability analysis. The Oxford Knee Score, Knee injury and Osteoarthritis 

Outcome Score—Physical Function Short Form, pain dur- ing activity score and knee extensor strength were used as comparator instruments. Measurements were obtained at baseline and 12 months after TKA. 

Results Appropriate test–retest reliability was found for all three tests. Intraclass correlation coe cient (ICC) for the 30-s CST was 0.90 (95% CI 0.68; 0.96), 40 m FPWT 0.93 (0.85; 0.96) and for the 10-step stair climb test (10-step SCT) 0.94 (0.89; 0.97). Adequate construct validity could not be con rmed for the three tests. For the 30-s CST, 42% of the prede ned hypotheses were con rmed; for the 40 m FPWT, 27% and for the 10-step SCT 36% were con rmed. The 40 m FPWT was found to be responsive with 75% of prede ned hypothesis con rmed, whereas the responsive- ness for the other tests could not be con rmed. For the 30 s CST and 10-step SCT, only 50% of hypotheses were confirmed.

Conclusions The three performance-based tests had good reliability, but poor construct validity and responsiveness in the assessment of function for the domains sit-to-stand movement, walking short distances and stair negotiation. The ndings of the present study do not justify their use for clinical practice. 

Level of evidence Level 1. Diagnostic study. Keywords Total knee arthroplasty · Osteoarthritis · 

Functional outcome · Performance-based measures