CASE 12119 Published on 04.09.2014

Bilateral medial oblique menisco-meniscal ligament with medial meniscal tear

Section

Musculoskeletal system

Case Type

Clinical Cases

Authors

Alan Sorani1, Sanjay Patel2

1. Alan Sorani, MSK Fellow,
The Royal Liverpool and Broadgreen Hospitals
2. Sanjay Patel,
MSK Consultant Radiologist,
Royal Derby Hospital,
Radiology Department,
Uttoxeter Road, Derby, DE22 3NE
Email: sanjay.patel7@nhs.net
Patient

40 years, male

Categories
Area of Interest Musculoskeletal system, Musculoskeletal joint ; Imaging Technique Conventional radiography, MR, MR-Angiography
Clinical History
A 40-year-old man presented to the accident and emergency department with right knee pain after suffering direct trauma to his right knee after tripping over a low brick wall.
On examination, there was a localised right knee joint tenderness but full range joint movement.
Imaging Findings
The plain radiograph appeared to be within normal limits.
MR imaging demonstrated a horizontal oblique tear in the posterior horn of the left medial meniscus. In addition, bilateral low-signal thin cordlike structures that originated from the anterior horn of the medial meniscus and inserted into the posterior horn of the lateral meniscus were seen. They extended through the intercondylar notch to lie anterior to the posterior cruciate ligament, in keeping with bilateral medial oblique menisci-meniscal ligaments.
Discussion
Background:

Oblique menisco-meniscal ligament (OMML) is an uncommon entity, which has not been extensively described in anatomy or radiology literature. This normal anatomical variant structure is also infrequently mentioned in arthroscopy literature.
It only accounts for 1-4% of all intermensical knee ligaments and its function is poorly understood but thought to contribute in meniscal stability [1-3]. The OMML is named after its anterior attachment site, thus medial oblique menisco-meniscal ligament attaches to the anterior horn of the medial meniscus and posterior horn of the lateral meniscus, while lateral oblique menisco-meniscal ligament attaches to the anterior horn of lateral meniscus and posterior horn of the medial meniscus. Both ligaments pass between anterior and posterior cruciate ligaments as traverse through the intercondylar notch.

Imaging perspectives:

In order to avoid erroneous radiological diagnosis and subsequent unnecessary surgical intervention, it is crucial for radiologists to be familiar with imaging appearances of the OMML when reporting knee magnetic resonance imaging (MRI) due to their resemblance to meniscal tear, in particular to flipped meniscal tear [4-6]. On the sagittal plane imaging this structure could give the appearances of double PCL sign which could be mistaken for an underlying bucket handle tear.

To correctly identify the OMML, one needs to be familiar with the appearances and the course of this structure as it extends from the anterior horn of one meniscus, traversing between both cruciate ligaments, to the posterior horn of the opposite meniscus as it passes through the intercondylar notch. In addition, one must ensure that the adjacent meniscus is of normal morphology at MR imaging in all three imaging planes, with no missing fragments. Once these criteria are met, the oblique menisco-meniscal ligament should be correctly identified at MR imaging as a normal anatomic variation rather than as a displaced meniscal fragment.

Teaching point:

Whilst oblique menisco-meniscal ligament is a rare entity which only accounts for 1-4% of all intermeniscal ligaments, it is pertinent to be aware of its imaging appearances and anatomical course in order to avoid erroneous diagnosis of meniscal tear and subsequent unnecessary surgical intervention.
Differential Diagnosis List
Bilateral medial oblique menisco-meniscal ligaments with left medial meniscal tear
Bucket handle meniscal tear
Displaced meniscal fragment
Final Diagnosis
Bilateral medial oblique menisco-meniscal ligaments with left medial meniscal tear
Case information
URL: https://www.eurorad.org/case/12119
DOI: 10.1594/EURORAD/CASE.12119
ISSN: 1563-4086