Postural Stability in Patients with Moderate Knee Osteoarthritis: Roles of Visual Feedback and Dynamic Perturbations

Background: Knee osteoarthritis is the most common joint disease and a leading cause of disability in old age. The present study aims to analyze the stability of standing with and without perturbation in patients with moderate knee osteoarthritis. Methods: Twenty-eight people (14 men with knee osteoarthritis and 14 healthy individuals) were evaluated for postural control in this observational crosssectional study. In standing tests, the effects of disease (osteoarthritis vs. healthy), vision (open vs. closed eyes), and support condition (quiet standing vs. on the unstable plate) on balance were studied. Results: The results showed that the presence of knee osteoarthritis significantly reduced the root mean square of hip joint flexion in patients compared to the control group (P= .024). The elimination of vision and reducing the base of support by standing on an unstable plate led to local instability in the joints close to the perturbation, especially the ankle (P<0.001). The center of pressure data also showed that the mean (P=0.034) and variability (P=0.003) of the anteriorposterior excursion was significantly higher in patients. Patients with knee osteoarthritis are more vulnerable to falling on an unstable plate. Conclusion: The body uses a postural stiffening strategy to prevent falling forward, especially on an unstable plate, and postural adjusting in the mediolateral direction. In rehabilitative treatments to prevent falls based on the sensory re-organization plans, e.g., rocking board, foam standing, game therapy, etc., it may be more efficient to focus on the distal joint muscles.