For a study, researchers sought to define the Western Ontario and McMaster Universities Osteoarthritis Index’s (WOMAC) meaningful within-patient change (MWPC). In 3 phase III clinical trials of tanezumab, a new medication for improving signs and symptoms of moderate-to-severe osteoarthritis (OA), delivered subcutaneously every 8 weeks, were independently assessed. At regular intervals, patients with moderate to severe hip or knee OA completed the WOMAC and global patient assessment of OA (PGA-OA). MWPC for WOMAC domains was determined using a repeated measures longitudinal model with change in WOMAC Pain, Physical Function, or Stiffness domain score as the outcome and change in PGA-OA as the anchor. About 688, 844, and 2,948 participants were available for analysis in the corresponding trials. The analysis revealed that a linear link between WOMAC domain changes and PGA-OA domain changes was validated and warranted. In addition, the associations between these variations were extremely similar in 2 trials and closed in the third. The estimated MWPC for the 3 WOMAC domains ranged from 0.84 to 1.16 (0–10 numeric rating scale) and 12.50 to 16.23%, which equated to a one-category change on the PGA-OA, depending on the study and domain. For a 2-category change, the respective numbers ranged from 1.68 to 2.31 and 25.01 to 32.46%. The outcomes established MWPCs for WOMAC domains at the individual patient level for individuals with moderate-to-severe hip or knee OA.