Longitudinal Trajectories of Pain Sensitization over Nine Years in People with or at Risk of Knee Osteoarthritis.

Pain sensitization is common in knee osteoarthritis (OA) and is associated with pain severity and functional limitations. Whether pain sensitization is induced by OA or may be an inherent trait remains unclear. We evaluated pain sensitization trajectories and their relations to symptoms in people with or at risk of knee OA. We used data from four study visits of the Multicenter Osteoarthritis (MOST) Study over a 9-year period. We agnostically identified pain sensitization trajectory groups defined by wrist and knee pressure pain thresholds (PPT) over nine years using group-based trajectory methods stratified by sex. We evaluated the relations of the wrist and knee PPT trajectory groups to WOMAC knee pain and function at the final visit using separate linear regression models. We included 1271 participants (mean age 65 years, 61% female, mean BMI 31 kg/m2) and identified three distinct trajectory groups in both women and men: low, moderate, and high PPTs. Overall, the PPT trajectories changed minimally over time in each group. Compared to the low PPT trajectory groups (the most sensitized groups), the moderate and high PPT groups had better WOMAC pain and function at the final assessment 9 years later. We identified stable but distinct pain sensitization trajectories over nine years despite likely changes in disease course and treatments over time, suggesting that individuals with knee OA may be predisposed to having different degrees of sensitization as an inherent trait, which in turn likely influences their pain experience and functional status.