To evaluate the mediating role of reduced muscle strength in the relationship between avoidance of activity and limitations in activities in patients with knee or hip osteoarthritis (OA).
A longitudinal cohort study with 5 years follow-up was conducted. Patients with knee or hip OA (n = 288) were recruited at rehabilitation centers and hospitals. Self-reported and performance based limitations in activities, avoidance of activity and muscle strength were assessed at baseline, 1, 2, 3 and 5 years follow-up. Generalized Estimating Equations (GEE) analyses were used to evaluate mediation.
In patients with knee OA, reduced knee extensor muscle strength mediated the relationship between avoidance of activity and limitations in activities. In patients with hip OA reduced hip abductor muscle strength mediates the relationship between avoidance of activity and limitations in activities.
The results of this longitudinal study support the theory that avoidance of activity leads to deterioration of muscle strength and consequently to more limitations in activities in patients with knee and hip OA.