Trajectories and Predictors of Weight-Bearing and Non-Weight-Bearing Pain in Knee Osteoarthritis: A 9-Year Follow-Up Study.

Objective: To identify distinct developmental trajectories of weight-bearing pain (WBP) and non-weight-bearing pain (NWBP) and examine the trajectory predictors in individuals with or at risk of knee osteoarthritis.

Methods: We included 971 participants from the Osteoarthritis Initiative whose baseline magnetic resonance imaging data and 9-year follow-up data on pain were available. We applied group-based trajectory modeling to identify WBP and NWBP trajectories over 9 years. Univariate and multivariate multinomial logistic regression analyses were performed to examine the predictors of identified trajectories.

Results: Three distinct WBP trajectories were identified: "no pain" (32.4%), "mild pain" (44.6%), and "moderate pain" (23%). Three distinct NWBP trajectories were identified: "no pain" (50.9%), "mild pain" (33.4%), and "moderate pain" (15.7%). In multivariate analyses, high body mass index, depression, multisite pain, radiographic knee OA, and comorbidities were associated with worse development trajectories for WBP and NWBP. Weak quadriceps strength and bone marrow lesion were only associated with worse WBP trajectories, whereas low education level was only associated with worse NWBP trajectories.

Conclusion: The developmental course of pain is heterogeneous in WBP or NWBP. Quadriceps strength and bone marrow leisure may be WBP-specific predictors, whereas education level may be a NWBP-specific predictor. The assessment of knee pain should be more accurate, which may help select appropriate therapeutic targets.