Abstract
BACKGROUND: Pain is the hallmark symptom of knee osteoarthritis (OA), and varies widely across individuals. Previous research has demonstrated both fluctuating and stable pain trajectories in knee OA using various time periods. Changes in pain assessed quarterly (i.e. 3-month intervals) in knee OA are relatively unknown. The current study aimed to investigate temporal variations in pain over a one and a half year period (18 months) based on quarterly characteristic pain assessments, and to examine differences in pain patterns by sociodemographic and baseline pain characteristics. METHODS: The sample included a prospective cohort of 188 participants (mean age 58 years; 63% female; 52% non-Hispanic Black) with or at risk for knee OA from an ongoing multisite investigation of ethnic/race group differences. Knee pain intensity was self-reported at baseline and quarterly over an18-month period. Baseline pain assessment also included frequency, duration, and total number of pain sites. Group-based trajectory modeling was used to identify distinct pain trajectories. Multinomial logistic regression was used to examine associations between sociodemographic characteristics, risk factors, and pain trajectory groups. RESULTS: Pain trajectories were relatively stable among a sample of adults with knee pain. Four distinct pain trajectories emerged in the overall sample, with the largest proportion of participants (35.1%) classified in the moderate-high pain group. There were significant relationships between age, education, income, ethnicity/race and trajectory group; with younger, less educated, lower income, and non-Hispanic Black participants had a greater representation in the highest pain trajectory group. CONCLUSIONS: Pain remained stable across a one and a half-year period in adults with or at risk for knee osteoarthritis, based on quarterly assessments. Certain sociodemographic variables (e.g. ethnicity/race, education, income, age) may contribute to an increased risk of experiencing greater pain.