Determination of the Factors Influencing Rupture of Baker’s Cysts in the Knee on Plain Radiographs and MRI

Purpose: We retrospectively compared plain radiographic and MR imaging findings of acutely ruptured and unruptured Baker’s cysts to determine which factors cause rupture of BCs. Materials and Methods: The MR findings for 44 Baker’s cysts (non-ruptured Baker’s cysts in 30 patients and ruptured Baker’s cysts in 14 patients) were evaluated. On the MR images, the characteristics of the Baker’s cysts, meniscal tears, and the quantity of joint effusions were evaluated. On plain radiographs, the grade of osteoarthritis of the affected knee was evaluated. Results: There was no statistically significant difference with respect to the size of Baker’s cysts, meniscal tears, and the grade of osteoarthritis between ruptured and unruptured Baker’s cysts. The wall thicknesses, inner signal intensities, inner septations, and the quantity of joint effusions were statistically different between the ruptured and unruptured Baker’s cysts. Conclusion: The most significant imaging finding which influences the rupture of a Baker’s cyst is the quantity of the joint effusion of the affected knee. In management of the patients with Baker’s cysts, the quantity of joint effusions should be kept in mind for preventative or treatment trials involving ruptured Baker’s cysts. Index words: Knee∙Baker cyst∙Rupture∙Magnetic resonance imaging (MRI) A Baker’s cyst (BC) or popliteal cyst shows a flui