Document Type : Original Articles


1 Department of Physical Therapy, Faculty of Medical Sciences, Tarbiat Modares University, Tehran 14115, Iran

2 Department of Physical Therapy, Faculty of Medical Sciences, Tarbiat Modares University


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.


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