Mechanistic pain profiling as a tool to predict the efficacy of 3-week nonsteroidal anti-inflammatory drugs plus paracetamol in patients with painful knee osteoarthritis.

Joint inflammation is present in a subpopulation of knee osteoarthritis (OA) patients. Proinflammatory cytokines are known to sensitize the peripheral and central pain pathways. This can be mechanistically assessed by pressure pain thresholds and temporal summation of pain (TSP). Nonsteroidal anti-inflammatory drugs (NSAIDs) combined with paracetamol are recommended as OA treatment. The current study hypothesized that evidence of central sensitization would predict poor responses to peripherally directed therapies in knee OA and therefore aimed to investigate the value of mechanistic pain profiling for predicting pain outcome of treatment with NSAIDs plus paracetamol. One hundred thirty-two patients received ibuprofen 1200 mg/daily, paracetamol 3 g/daily, and pantoprazole 20 mg/daily for 3 weeks. Before administration, cuff pain detection, tolerance threshold, and TSP were assessed. Worst pain within the last 24 hours and pain during activity (visual analogue scales) were assessed before and after treatment. Facilitated TSP was found at baseline in the nonresponders to the 3-weeks treatment as compared to responders for both the 30% and 50% pain alleviation criteria (P < 0.02). Linear regression models identified facilitated TSP (P < 0.01) and low clinical pain scores (P < 0.001) as independent factors for prediction of poor pain alleviation by the treatment. In conclusion, this study found that mechanistic pain profiling can predict pain alleviation of NSAIDs and paracetamol. Facilitated TSP and low clinical pain scores before treatment are independent predictors of poor pain alleviation after NSAIDs and paracetamol. This study adds to the growing evidence that a subgroup of knee OA patients with manifested central sensitization may require special management attention.