Meaningful changes in physical function and pain in patients with knee osteoarthritis

BACKGROUND: This study aims to establish meaningful within-person change (MWPC) thresholds for the Total Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC®), its Physical Function (PF) subscale, and the Visual Analog Scale (VAS) for Pain, in patients with knee osteoarthritis (OA). A secondary objective is to evaluate the effectiveness of a single injection of autologous culture-expanded adipose tissue-derived mesenchymal stem cells (ADMSCs) using these thresholds. METHODOLOGY: The study included 252 patients with knee OA enrolled in a clinical trial. An anchor-based predictive modeling approach, using KOOS-12, SF-36, and IKDC scores with literature-based cut-offs, was applied to determine MWPC thresholds for WOMAC and VAS Pain. MWPC thresholds were derived from both the ADMSCs injection and Control (autoserum) groups at 3- and 6-month follow-ups. Treatment effectiveness was assessed by comparing MWPC range with between-group differences and within-person changes. RESULTS: MWPC thresholds were identified as follows: 5–17 points for WOMAC Total, 4–12 points for WOMAC PF, and 8–14 points for VAS Pain (all on 0–100 scales). The adjusted differences between the ADMSCs injection and Control (autoserum) groups of all three measures (3 months: WOMAC Total 5.9, WOMAC Function 4.2, VAS Pain 8.6; 6 months: WOMAC Total 9.3, WOMAC Function 6.5, VAS Pain 11.7) were within each corresponding MWPC threshold range. CONCLUSIONS: The proposed MWPC thresholds could be beneficial for healthcare professionals as a tool to identify meaningful change in physical function and pain in response to treatment and evaluate the meaningfulness of treatment benefits.