Latent Transition Analysis of Pain Phenotypes in People at Risk of Knee Osteoarthritis: The MOST cohort study

Pain phenotypes (PP) have been identified across different stages of knee osteoarthritis (KOA) and understanding the stability of PPs prior to the development of symptomatic KOA can help to inform preventative strategies. We aimed to identify PPs and their transitions in people without radiographic KOA and profile participant characteristics. Data from 5 - (T1), 7- (T2) and 12-year (T3) visits from the Multicenter Osteoarthritis Study (MOST) were used. Individuals with Kellgren-Lawrence grade 0 and knee pain ≤30/100 at T1 were sampled. PP variables included pressure pain thresholds, temporal summation (with method changed at T3), depressive symptoms, pain catastrophizing, sleep quality, and widespread pain. Latent Transition Analysis using Bayesian Information Criteria informed class numbers and transitions. Unconstrained, constrained, and modified constrained models (conditional response probabilities fixed for indicator variables except for TS) were compared for fit. Participant characteristics were used to profile class membership. 348 individuals (59% females), mean age (SD): 59.3 (6.7) were included. The optimal model fit for data across T1-T3 was a "modified" constrained model with 3 classes (class 1: low pain burden, class 2: high pain sensitization, class 3: high psychological burden). Classes were similar over time except for the increased probability of TS at T3. Most (86%) participants remained in the same class; only 14% transitioned overtime. Distinct PPs were identified in those at risk of KOA that remained stable over time, suggesting these trait-like features may require consideration for comprehensive management of the symptom experience.