Responsiveness and minimal important changes of the OARSI core set of performance-based measures in patients with knee osteoarthritis following physiotherapy intervention

Purpose The Osteoarthritis Research Society International has recommended a core set of performance-based tests of physical function for use in knee osteoarthritis (OA) patients. The core set includes 30-second chair stand test (30-s CST), 4 x 10 m fast-paced walk test (40-m FPWT), and a stair climb test. This study aimed to evaluate responsiveness and minimal important changes (MICs) of these performance-based measures in knee OA patients following physiotherapy. Methods Sixty patients with knee OA, undergoing 4-week physiotherapy performed 30-s CST, 40-m FPWT, and 4-step stair climb test (4-step SCT) at pre- and post-intervention. Patients also completed the 7-point global rating scale as an external anchor at post-intervention. Responsiveness was evaluated using receiver operating characteristics curve and correlation analysis. Results All three performance-based measures of physical function showed area under the curve > 0.70. Correlation analysis showed relationship of 30-s CST, 40-m FPWT, and 4-Step SCT with the external anchor fell within moderate to good range (Spearman = 0.43-0.63). Furthermore, MIC values reflecting improvement for 30-s CST, 40-m FPWT, and 4-Step SCT were 2.5, 0.21, and 3.21, respectively. Conclusion Our findings demonstrated all three performance-based measures have good responsiveness to measure improvement in physical functions of knee OA patients following physiotherapy. The MIC reflecting improvement can help clinicians and researchers to make a decision based on the clinical significance of improvements in patients' functional status.