The Sonographic Spectrum of Baker Cysts

Baker cysts are the most common pathologic finding in the sonography of the popliteal fossa. They have a wide range of sonographic appearances. Some of them may need to be recognized and differentiated from other popliteal lesions. Therefore, familiarity with their different imaging appearances is useful for clinical practice. This review summarized different presentations of Baker cysts. They are described in several categories, organized according to their shape and formation: typical Baker cysts and their mild variations, atypical small Baker cysts, ʎ-shaped Baker cysts and their related variations, Baker cysts with extension into nearby muscles, and Baker cysts with complications. The related differentiations are included in each category. The pathogenesis of Baker cysts is also discussed.