Determinants of daily pain trajectories and relationship with pain acceptability in hip and knee osteoarthritis. A national prospective cohort study on 886 patients.

Objectives: To study daily pain trajectories (DPT) in patients with knee (KOA) and hip osteoarthritis (HOA) over a one-month period and identify relationships with patients characteristics and acceptability.

Methods: This prospective, multicenter cohort study was conducted in France by 602 GPs, on outpatients, with painful KOA or HOA. Patients were asked to fill-in a 28-days daily pain diary. DPT were determined by the difference between daily pain and mean pain over 28 days. Pain peaks were defined as an increase of more than 1 point above the mean for up to three consecutive days. The number of pain peaks over the 28 day period allowed classifying the patient's pain trajectory as either "stable" or "unstable". A logistic regression model was used to identify predicting factors associated with stable pain profile.

Results: Overall, 1645 patients were included and 886 were analyzed, (56% women, 67.8 years, BMI 27.6 kg/m, pain 6.0, KOA 71.3%). At one month, stable DPT was found in 59.5% of the patients whatever OA location. In HOA, a shorter duration of disease and pain, a greater disability and in KOA, a more recent disease, morning stiffness ≥ 15 minutes and flare-up were independent factors associated with "stable" DPT. At one month, acceptable pain state was more frequent (65.4%) in patients with stable profiles.

Conclusion: In lower limb OA, pain is mostly stable over a 28-days period. Pain is better accepted when stable, with different determining factors according location. DPT should be considered when establishing HOA and KOA management.