Background The avoidance model explains how behavioral mechanisms may lead to activity limitations in patients with osteoarthritis (OA) of the knee or hip. According to this model, the patient with OA experiences pain during activities. This leads to the expectation that renewed activity will cause greater pain, resulting in avoidance of activities. Avoidance of activities results in physical decline, most notably muscle weakness. Muscle weakness leads to an increase in activity limitations. In addition, it is hypothesized that psychological distress enhances the tendency to avoid activities, leading to muscle weakness and activity limitations.
Objectives To review the scientific evidence for the validity of the avoidance model in patients with knee and hip OA.
Methods A literature search was conducted in four electronic databases. Selection criteria included: knee or hip OA or pain; examination of consecutive components of the avoidance model; observational study; original research report. The methodological quality of the selected articles was assessed, and qualitative data synthesis identified levels of evidence.
Results Sixty studies were included. In patients with knee OA, strong evidence was found that avoidance of activities is associated with activity limitations via muscle weakness (mediation by muscle weakness); strong evidence was found for an association between muscle weakness and activity limitations; and weak evidence was found that pain and psychological distress are associated with muscle weakness via avoidance (mediation by avoidance). In patients with hip OA, weak evidence was found for mediation by muscle weakness; and strong evidence was found for an association between muscle weakness and activity limitations.
Conclusions In patients with knee OA, the association between avoidance of activities and activity limitations is for a substantial part explained by muscle weakness. In both patients with knee OA and patients with hip OA, muscle weakness is associated with activity limitations. These results emphasize the importance of muscle strength in maintenance of activities. More research is needed on the consecutive associations between pain or psychological distress, avoidance of activities and muscle weakness, and to confirm causal relationships.
Disclosure of Interest None declared