The Inverse OARSI-OMERACT Criteria Is a Valid Indicator of the Clinical Worsening of Knee Osteoarthritis: Data From the Osteoarthritis Initiative

Abstract

OBJECTIVE: We assessed if the inverse Osteoarthritis Research Society International (OARSI) and Outcome Measures in Rheumatology (OMERACT) criteria relate to concurrent radiographic knee osteoarthritis (KOA) progression and decline in walking speed, as well as future knee replacement. METHODS: We conducted knee-based analyses of data from the Osteoarthritis Initiative. All knees had symptomatic OA: at least doubtful radiographic KOA (Kellgren-Lawrence grade > /= 1) and knee pain > /= 10/100 (Western Ontario and McMaster Universities Osteoarthritis Index pain) at the 12-month visit. The inverse of the OARSI-OMERACT responder criteria depended on knee pain and function, and global assessment of knee impact. We used generalized linear mixed models to assess the relationship of the inverse OARSI-OMERACT criteria over 2 years (i.e., 12-month and 36-month visits) with worsening radiographic severity (any increase in Kellgren-Lawrence grade from 12 months to 36 months) and decline in self-selected 20-m walking speed of > /= 0.1m/s (from 12 months to 36 months). We used a Cox model to assess time to knee replacement during the 6 years after the 36-month visit as an outcome. RESULTS: Among the 1746 analyzed, 19% met the inverse OARSI-OMERACT criteria. Meeting the inverse OARSI-OMERACT criteria was associated with almost double the odds of experiencing concurrent worsening in radiographic KOA severity (OR 1.89, 95% CI 1.32-2.70) or decline in walking speed (OR 1.82, 95% CI 1.37-2.40). A knee meeting the inverse OARSI-OMERACT criteria was more likely to receive a knee replacement after the 36-month visit (23%) compared with a nonresponder (10%; HR 2.54, 95% CI 1.89-3.41). CONCLUSION: The inverse OARSI-OMERACT criteria for worsening among people with KOA had good construct validity in relation to clinically relevant outcomes.