Identification of pain categories associated with change in pain in patients receiving placebo: Data from two phase 3 randomized clinical trials in symptomatic knee osteoarthritis

Pain is the principal clinical symptom of osteoarthritis (OA), and development of safe and effective analgesics for OA pain is needed. Drug development of new analgesics for OA pain is impaired by substantial change in pain in patients receiving placebo, and more data describing clinical characteristics and pain categories particularly associated with this phenomenon is needed.