Longitudinal Assessment of Pain Management Among the Employed Japanese Population with Knee Osteoarthritis

PURPOSE: To assess comorbidity burden and pain-management patterns among working-aged patients with knee osteoarthritis only (KOA/O) and patients with knee osteoarthritis plus osteoarthritis at another site (KOA/+) in Japan. PATIENTS AND METHODS: Retrospective claims data analysis was conducted using the Japan Medical Data Center database. Working-aged adults (aged 40 to 71 years) with 5 years of follow-up and diagnosed with knee osteoarthritis (KOA) between January 1, 2011, and December 31, 2012, were evaluated. The first claim with a KOA diagnosis defined the index date. Patients were divided into two mutually exclusive cohorts: KOA/O and KOA/+. Longitudinal pain-management patterns during each year of follow-up were analyzed. RESULTS: A total of 2542 patients met study criteria: 1575 KOA/O and 967 KOA/+. Mean age and number of comorbidities were higher among the KOA/+ versus KOA/O cohort. Pharmaceutical treatment was received by 91.5% of patients in the KOA/+ compared with 85.1% of patients in the KOA/O cohort during the first year of follow-up. The most common pharmacological treatment received during the first year of follow-up was either topical or oral nonsteroidal anti-inflammatory drugs for both cohorts. During each year of follow-up, the KOA/+ cohort had greater proportion of patients with at least one health-care encounter (ie, hospital admissions, outpatient and pharmacy visits) and higher direct medical costs compared with the KOA/O cohort. CONCLUSION: This study demonstrates that a greater proportion of the working population with KOA/+ received pain-related treatment compared with patients with KOA/O. Further studies are necessary to evaluate appropriate pain management for both KOA only and KOA with other sites.