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CHECKing activity limitations in persons with early osteoarthritis of the knee or hip: Course, prognosis and underlying mechanisms

Objective. It has been hypothesized (1) that pain and low vitality lead to an increase in avoidance of activities in persons with early symptomatic knee osteoarthritis (OA), and (2) that avoidance of activities leads to an increase in activity limitations. The present study aimed to evaluate these hypotheses. Methods. Baseline, 2-year and 5-year follow-up data of 828 participants from the Cohort Hip and Cohort Knee (CHECK) study with early symptomatic knee OA were used. Autoregressive generalized estimating equations (GEE) and linear regression models were used to analyse the longitudinal and cross-sectional associations between self-reported knee pain, vitality, pain-related avoidance of activities and activity limitations. The models were adjusted for the covariates age, gender, education level, body-mass index, comorbidity, radiographic severity, and hip pain. Results. (1) In longitudinal analyses, knee pain and vitality predicted a subsequent increase in avoidance of activities. (2) Pain-related avoidance of activities predicted a subsequent increase in activity limitations, however this relationship lost statistical signiﬁcance (p = 0.089) after adjustment for covariates. Cross-sectional analyses showed strong relationships between knee pain, low vitality, pain-related avoidance of activities and activity limitations at all time-points. Conclusions. In persons with early symptomatic knee OA, knee pain and low vitality lead to a subsequent increase in avoidance of activities. Pain-related avoidance of activities is related to activity limitations at inception of symptoms but also years later. Therefore, it can be recommended to monitor and target avoidance of activities at various stages of the disease.