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

Knowledge of patellofemoral osteoarthritis (OA) pain trajectories is vital to helping clinicians and patients make shared disease-specific decisions regarding treatment options and coping strategies. To describe the pain trajectories of people living with patellofemoral OA who present to a chronic care management program, and to explore baseline characteristics associated with different trajectories. In this prospective longitudinal cohort study, 88 participants who presented to a chronic care management program reported their worst pain over the previous week at baseline and at 6, 12, 18, and 26 weeks using a 10-cm visual analog 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. Individuals in class 1 (28%) exhibited high, persistent pain from baseline (7.8 ± 1.7 cm), which continued over time (P = .52). Class 2 (57%) displayed moderate baseline pain (4.8 ± 1.8 cm), which also remained persistent (P = .97). Individuals in class 3 (15%) showed low, improving pain (baseline pain, 2.6 ± 1.2 cm) over time (P = .017). At baseline, poor Knee injury and Osteoarthritis Outcome Score (KOOS) scores, local and proximal sensitivity to pressure, and lower knee extensor strength were associated with increased odds of following the high-pain trajectory (range [95% confidence interval], 1.03 [1.00, 1.07] to 16.24 [2.53, 104.34]). Distinct pain trajectories appear to exist in people with patellofemoral OA presenting to a chronic care management program. Baseline variables may be useful for identifying individuals at risk of poorer prognosis. Larger studies are needed to confirm the efficacy of this finding. Prognosis, level 2b. J Orthop Sports Phys Ther 2019;49(1):5-16. Epub 12 Sep 2018. doi:10.2519/jospt.2019.8354.