The Frequency of Baker's Cysts Associated with Meniscal Tears

Abstract

We reviewed the films of 1760 patients who had mag netic resonance image scanning of the knee joint to assess the most common pathologic changes associ ated with an incidental finding of a Baker's cyst. Of the 1760 knees scanned, Baker's cysts were noted in 238. The cysts were classified as small (55%), medium (30%), or large (15%) and were primarily found on the medial side of the knee (94%). The menisci were eval uated and changes were classified as complete tears, where signal contacts the surface, or degenerative intrasubstance tears. One hundred eleven (47%) com plete meniscal tears were found, and 88 (37%) degen erative tears. The majority of tears were found in the posterior horn of the medial meniscus (65 complete tears and 45 degenerative tears). Thus, 199 tears were found in 170 knees, and 106 of the 170 knees (62%) had tears of the posterior horn of the medial meniscus. Baker's cysts are frequent findings on physical exam inations and on magnetic resonance imaging scans of the knee. They are thought to be due to intraarticular pathologic changes, usually posterior meniscal tears. This study documents the association between Baker's cysts and meniscal tears and notes that a complete tear is not necessary for the cyst to be present.