Exploratory Study of 6-month Pain Trajectories in Individuals With Predominant Patellofemoral Osteoarthritis: A Cohort Study.

Study Design Prospective longitudinal cohort study. Background Knowledge of patellofemoral (PF) osteoarthritis (OA) pain trajectories is vital for clinicians and patients to make disease-specific decisions regarding treatment options and tailor coping strategies. Objectives To describe pain trajectories of people living with PF OA presenting to a chronic care management program. Second, to explore baseline characteristics associated with different trajectories. Methods Eighty-eight participants presenting to a chronic care management program reported their worst pain over the previous week at baseline, 6, 12, 18 and 26 weeks using a 10-cm visual analogue scale. Trajectories (classes) were identified using latent class growth analysis. Demographics, pain, physical performance, strength, quality of life, mental health and lower limb/foot structural measures obtained at baseline were assessed for association with trajectory class membership. Results Class 1 (28%) exhibiting high persistent pain from baseline (6.8cm ± 1.7cm), and persisting through time (p=0.52). Class 2 (57%) exhibited moderate baseline pain (4.8cm ± 1.7cm), which also remained persistent (p=0.97). Individuals in class 3 (15%) exhibited low improving pain (baseline pain: 2.6cm ± 1.2cm) through time (p=0.017). Baseline measures of poor Knee injury and Osteoarthritis Outcome Scores, local and proximal sensitivity to pressure and weaker knee extensors were associated with increased odds (range: 1.03 (1.0, 1.07) to 16.24 (2.53, 104.34)) of following the high pain trajectory. Conclusion In people with PF OA presenting to a chronic care management program, distinct pain trajectories appear to exist. Baseline variables may be useful for identifying individuals at risk of poorer prognosis. Larger studies are needed to confirm such utility. Level of Evidence Prognosis, Level 2b. J Orthop Sports Phys Ther, Epub 12 Sep 2018. doi:10.2519/jospt.2019.8354.