Purpose: Arthritis pain symptoms do not correlate with radiographic damage in knee osteoarthritis, and central pain sensitization (neurobiological alterations in pain signaling) may play a role in some patients. Some patients with chronic OA have suboptimal pain relief and the comorbid prevalence of pain sensitivity phenotypes in OA patients is unknown. Prospective studies may help identify predictors of suboptimal pain management, and a composite index may be useful as part of an initial assessment. Methods: The SOAR (Pain sensitivity in osteoarthritis research) cohort is a prospective, longitudinal study of patients with chronic knee pain and radiographic osteoarthritis. At baseline, patients completed selfreport questionnaires, including the PainDETECT survey, Brief Pain Inventory, and a body map. Quantitative sensory testing and conditioned pain modulation was evaluated using the MAST device. Descriptive statistics and correlational analyses examined the results. Results: 60 patients were enrolled at the time of the evaluation; enrollment is ongoing for this cohort. Patient scores on pain assessments were normally distributed. Pain scores did not correlate with radiographic severity. A composite index score for centrally mediated pain was directly correlated with baseline pain intensity and neuropathic pain complaints, Differences were noted in pressure pain thresholds between men and women, but no gender differences were seen in conditioned pain modulation. The impact of caffeine intake on QST results was assessed. Conclusions: In a medically managed cohort of patients with knee osteoarthritis, radiographic indices did not correlate with pain scores. A higher composite index score of centrally mediated pain complaints and symptoms was correlated with self-report of higher pain and more neuropathic pain descriptors. Future studies on predictors of pressure pain thresholds and limited conditioned pain modulation may help identify patients who preferentially respond to targeted therapies. Pain: Pathophysiology.
Phillips, K. (2014). Pain mechanisms in OA: quantitative sensory testing and patient reported outcomes. Osteoarthritis and Cartilage, 22, S416. https://doi.org/10.1016/j.joca.2014.02.784