Wrisberg rip

Wrisberg rips, also known as zip tears or zipper tears, are longitudinal vertical meniscal tears. They occur at the junction of the ligament of Wrisberg and the posterior horn of the lateral meniscus and are commonly associated with anterior cruciate ligament tears ¹. 

Pathology

The ligament of Wrisberg is attached to the lateral aspect of the medial femoral condyle and to the posterior horn of the lateral meniscus, coursing posteriorly to the PCL. In case of the ACL tear, anterior tibial translation occurs, resulting in traction of the ligament of Wrisberg against the PCL and tearing a longitudinal fragment of the lateral meniscus, hence the term 'zip tear'.

Location

It occurs at the posterior horn of the lateral meniscus, starting from the posterior root and extending anteriorly.

Radiographic features

MRI

It is visible on fluid-sensitive sequences, best visualized on sagittal and often on axial images, as a cleft extending anteriorly from the posterior root of the lateral meniscus on several consecutive slices.

Practical points

The pitfall in diagnosing this type of tear is that normally there is a cleft at the attachment site of the ligament of Wrisberg to the posterior horn of the lateral meniscus, which can be mistaken for a tear. Due to variability in the ligament attachment site, this cleft can extend variably far, and as a result the discrimination between a true tear and a 'pseudo-tear' may pose a challenge. It has been postulated by some authors that the average attachment site lies approximately 14 mm laterally from the lateral edge of the PCL ¹, and that any cleft extending farther is suspicious for a tear.