Ghost meniscus

A ghost meniscus, also known as the empty meniscus sign, refers to either a complete radial tear that has transected the meniscus, a displaced root avulsion or, alternatively, be evident in from a previous meniscectomy.

Terminology

Defined by the presence of a meniscus which disappears then reappears like a 'ghost' on consecutive sagittal sequences. This occurs when the slice plane is exactly in line with the meniscal tear/ gap, and on MRI produces complete or near-complete signal loss on from the involved meniscus from partial volume averaging or even a complete absence of the meniscus when there is a large-sized defect.

The terms complete radial tear and transection of the meniscus are used interchangeably to describe the same pathology.

Practical points

• complete radial tears and root avulsions should be suspected if the central third of the meniscus is extruded
• stating the quality of the articular cartilage adjacent to the tear is important to guide further management
• the posterior third and posterior horns are more commonly affected
• often the extruded central third of the meniscus will cause the medial collateral ligament to bow outwards