Introduction: Knee osteoarthritis often causes disability due to the pain it causes and affects a person's quality of life.The purpose of this study is to investigate the effect of ankle-foot-orthosis with and without lateral wedge on pain, function and displacement of the center of pressure in patients with the medial compartment knee osteoarthritis.
Methodology: The research method was quasi-experimental with a pre-test and post-test design. This study was conducted on  patients with medial compartment knee osteoarthritis in the age range of  to  years as available sampling. Demographic information and Womac questionnaire were completed and the displacement of the center of pressure in the internal-external plane was recorded by the Kistler force plate device, in three situations: bare feet, ankle-foot orthosis with lateral wedge and ankle-foot orthosis without lateral wedge. The obtained data were analyzed using SPSS software. Shapiro-Wilk test was used to check the conformity of distribution of quantitative variables with normal distribution. According to the normality (p>0.05), variance analysis tests, multiple comparisons and generalized linear models were used for data analysis.
Results:  patients participating in this study were examined in three situations, and the pain of the patients in the state of using the orthosis with the lateral wedge was significantly reduced (p=), the function of the patients was better in the state of using the orthosis with the lateral wedge. (p=), but the displacement of the center of pressure in the case of using the orthosis without wedge had a significant decrease (p=).
Conclusion: the use of an orthosis with an lateral wedge was effective in improving pain and function, but the use of an orthosis without an wedge led to a reduction in the displacement of the center of pressure in the internal-external plane. Therefore, it will probably reduce the knee adduction moment.