Identifying trajectories of pain severity in early symptomatic knee osteoarthritis: A 5-year followup of the cohort hip and cohort knee (CHECK) study

Objective. To identify subgroups of pain trajectories in patients with symptomatic knee osteoarthritis (OA), and to explain these different trajectories by patient characteristics, lifestyle, and coping factors, as well as radiographic features. Methods. Longitudinal data of pain severity (0-10) from 5 years of followup of the CHECK (Cohort Hip and Cohort Knee) study was used. Latent class growth analysis identified homogeneous subgroups with distinct trajectories of pain. Multinomial regression analysis was used to examine different lifestyle and coping characteristics between the trajectories. Results. In longitudinal pain data of 5 years of followup in 705 participants, 3 pain trajectories were identified: marginal, mild, and moderate pain trajectories. Compared with the marginal pain trajectory, the mild and moderate pain trajectories can be characterized by the following baseline variables: body mass index (BMI) > 25, additional hip pain, low education level, using the coping strategy "worrying," and having ≥ 3 comorbidities. Moderate pain trajectory can be supplemented with the Kellgren-Lawrence grading scale grade ≥ 2 radiological change. Conclusion. Three trajectories of pain were identified. Participants with a BMI > 25, secondary school as highest education level, having at least 3 comorbidities, additional hip pain, and/or whose coping style is worrying are more likely to develop a moderate or mild pain trajectory compared with those without these characteristics. In the management of knee pain in people with early symptomatic OA, attention should also be given to additional factors such as hip pain, other comorbidities, passive coping strategy, and obesity.