MRI appearance of meniscal cysts.

ABSTRACT

PURPOSE: The purpose of this study was to review the MRI criteria for the distinction of meniscal cysts from other cystic lesions in the knee so that appropriate treatment may be planned. DESIGN: A retrospective review of 62 knee MRI scans possibly showing meniscal cysts was performed. The type of meniscal tear, the appearance of the connection between the cyst and the meniscal tear, and the location, size, morphology, and signal characteristics of the meniscal cysts were recorded. Other types of fluid collections that had been mistaken for meniscal cysts were described. PATIENTS Sixty-two patients were studied, ages 16-79 years, 61% male, 39% female. RESULTS AND CONCLUSIONS: Most of the meniscal cysts (91%) occurred immediately adjacent to the meniscal tear (98% horizontal cleavage tears, 49% anterolateral), with the tear leading directly into the cysts. In two cases, the cyst had dissected into the soft tissues distant from the meniscus and a connecting stalk was visualized. Fluid collections in normal bursae and recesses that had been mistaken for meniscal cysts had no direct connection to a meniscal tear. MRI can be used to distinguish meniscal cysts from other fluid collections that may mimic meniscal cysts. Pitfalls can be avoided by familiarity with the normal bursal and capsular anatomy, and by the application of specific diagnostic criteria.