MR imaging of the knee: pseudotear of the lateral meniscus caused by the meniscofemoral ligament

Abstract

Sagittal MR images of the knee often show a linear band of increased signal in the medial aspect of the posterior horn of the lateral meniscus that can be confused with a meniscal tear. This pseudotear is due to the meniscal insertion of the meniscofemoral ligament. To study the normal appearance of the medial aspect of the posterior horn of the lateral meniscus, we analyzed 109 MR examinations and correlated the findings with the results of arthroscopy. The meniscofemoral ligament was visualized in 54 cases (50%), and in 42 cases (39%) it caused the appearance of a pseudotear on sagittal images. The pseudotear had one of two orientations. The most common (35/42) was an oblique orientation coursing from the superior surface posteriorly and inferiorly. The other (7/42) was a more vertical orientation parallel to the base of the meniscus. Knowledge of the characteristic location and orientation of the meniscofemoral ligament should help to distinguish it from a true meniscal tear on MR images.