Clinical History
The presence of intrameniscal high signal intensity lines on both menisci, and an intrasubstance oedema of the anterior cruciate ligament was found on the MR examination of a 37-year-old male
patient, with a previous injury of his right knee. A linear structure of low signal intensity, on all sequences, was found connecting the posterior horn of the lateral meniscus with the anterior horn
of the medial meniscus.
Imaging Findings
A 37-year-old male patient was admitted to our hospital because of a previous injury to his right knee. An MRI of his knee was performed in order to show any internal derangement of the joint. It was
found that the medial meniscus had an intrasubstance grade I high signal intensity line and the lateral meniscus had an intrasubstance grade II high signal intensity line. The anterior cruciate
ligament was not ruptured but there was a high signal intensity on the T2W fat-suppressed images, suggesting intrasubstance oedema. There was a linear structure of low signal intensity, on all
sequences, located just above the intercondylar eminence. This structure seemed to connect the anterior horn of the medial meniscus with the posterior horn of the lateral meniscus. On performing an
arthroscopy, it was found that the structure originated from the anterior horn of the medial meniscus and extended over the intercondylar notch to insert into the posterior horn of the lateral
meniscus, representing a medial oblique menisco-meniscal ligament.
Discussion
In the medical literature, four different types of menisco-meniscal ligaments have been described [1–4]. The most frequently present intermeniscal ligament is the anterior transverse ligament
(Fig.1a) with a reported frequency of 58% [1]. The posterior transverse ligament follows, with a reported frequency of 1%–4% [1]. The remaining ligamentous structures are the medial and the
lateral oblique menisco-meniscal ligaments, which have a frequency of occurrence about 1% [1]. Each one is named after its anterior meniscal origin. The medial oblique menisco-meniscal ligament
(Fig.1b) is the one that connects the anterior horn of the medial meniscus with the posterior horn of the lateral meniscus, and the lateral menisco-meniscal ligament (Fig.1c) is the one that connects
the anterior horn of the lateral meniscus with the posterior horn of the medial meniscus [3]. The anterior transverse ligament has been described as a potential pitfall of a meniscal tear [3]. Other
normal anatomical structures that may mimic meniscal tears include the meniscofemoral ligaments and the popliteal tendon. The oblique menisco-meniscal ligament may be misinterpreted as a
bucket-handle type of tear of the meniscus or even a rupture of the anterior (Fig.2) or posterior cruciate ligament [2, 3]. In our case, we correctly interpreted the medial oblique menisco-meniscal
ligament because we could follow it on the coronal images (Fig.3), extending from the anterior horn of the medial meniscus and over the intercondylar notch inserting into the posterior horn of the
lateral meniscus. Also, the menisci were shown to have a normal shape on both coronal and sagittal images with no missing parts.
Differential Diagnosis List
Medial oblique menisco-meniscal ligament.
Final Diagnosis
Medial oblique menisco-meniscal ligament.
