The association between the flat feet and the symptoms of knee osteoarthritis

Objective: The purpose of this study was to assess the association between the flat feet and the symptoms of knee osteoarthritis (OA). Methods: 95 participants with knee osteoarthritis were recruited for this study. Knee osteoarthritis was evaluated using a combination of Kellgren-Lawrence (K-L) grade, femoral-tibial angle (FTA), knee pain and physical function. The Arch Index (AI) was used to assess the severity of flat feet, with subjects being divided into groups with no flat feet, mild flat feet and severe flat feet. A chi-square test, continuous variable t test and Mann-Whitney U test were used to compare differences in K-L grade, knee pain, physical function and femoral-tibial angle. Regression analysis was performed to assess the correlation between the flat feet and the characteristics of knee osteoarthritis. Results: Flat feet was associated with a significantly increased risk of having a larger varus angle (beta: -2.306; 95% confidence interval (CI): -3.703, -0.909; p = 0.001), higher pain score (beta: 0.356; 95% CI: 0.130, 0.582; p = 0.002) and greater loss of physical function (beta: 0.281; 95% CI: 0.071, 0.491; p = 0.009). Severe grades of flat feet were associated with an increased risk of pain (beta: -0.289; 95% CI: -0.543, -0.035; p = 0.026). However, the severity of flat feet was not associated with K-L grade, FTA or physical function. Conclusion: There was a significant association between the presence of flat feet and symptoms of knee OA, and severe flat feet was found to aggravate OA-related knee pain. Active treatment to correct flat feet is recommended to relieve symptoms associated with knee OA. Level of Evidence: Level II