The purpose of this study is to investigate the utility of fentanyl matrix for the treatment of pain due to osteoarthritis (OA) of knee or hip, which was not adequately controlled by non-opioid analgesic (e.g. NSAIDs or COX-II inhibitors) or weak opioids [tramadol HClacetaminophen, tramadol or codeine (or combinations with acetaminophen/ibuprofen)].