Frailty predicts knee pain trajectory over 9 years: results from the Osteoarthritis Initiative

Frailty is a multisystem syndrome and its relationship with symptomatic osteoarthritis has been reported. We aimed to identify trajectories of knee pain in a large prospective cohort and to describe the effect of frailty status at baseline on the pain trajectories over 9 years.We included 4419 participants (mean age 61.3 years, 58% female) from the Osteoarthritis Initiative cohort. Participants were classified as 'no frailty', 'pre-frailty', or 'frailty' at baseline, based on five characteristics (i.e., unintentional weight loss, exhaustion, weak energy, slow gait speed, and low physical activity). Knee pain was evaluated annually using the Western Ontario and McMaster Universities Osteoarthritis Index pain subscale (0-20) from baseline to 9 years.Of the participants included, 38.4%, 55.4%, and 6.3% were classified as 'no frailty', 'pre-frailty', and 'frailty', respectively. Five pain trajectories were identified: 'No pain' (n = 1010, 22.8%), 'Mild pain' (n = 1656, 37.3%), 'Moderate pain' (n = 1149, 26.0%), 'Severe pain' (n = 477, 10.9%), and 'Very Severe pain' (n = 127, 3.0%). Compared to participants with no frailty, those with pre-frailty and frailty were more likely to have more severe pain trajectories (pre-frailty: odds ratios (ORs) 1.5 to 2.1; frailty: ORs 1.5 to 5.0), after adjusting for potential confounders. Further analyses indicated that the associations between frailty and pain were mainly driven by exhaustion, slow gait speed, and weak energy.Approximately two-thirds of middle-aged and older adults were frail or pre-frail. The role of frailty in predicting pain trajectories suggests that frailty may be an important treatment target for knee pain.