MENISCAL AND CRUCIATE ANATOMY

MEDIAL MENISCUS
The medial meniscus is C shaped.
Its central attachments lie on either side of the tibial spines and
are outside the central attachments of the lateral meniscus.
The medial meniscus has strong peripheral attachments to the deep fibres of the medial collateral ligament and posteriorly
It is asymmetrical in the sagittal plane with the posterior portion of the meniscus being larger and taller than the anterior portion.
LATERAL MENISCUS
The lateral meniscus is rounder and its central attachments lie inside those of the medial meniscus.
It has weak peripheral attachments making it more mobile and allowing it to move anteroposterior in conjunction with the external rotation at full knee extension.
The popliteus tendon runs across its posterolateral margin to the popliteus tunnel which lies immediately adjacent to the lateral meniscus.

Coronal views which are useful for assessing the posterior portions of the meniscal bodies and the posterior attachments of the menisci which are called the meniscal struts. The central portion of the posterior knee is complex and the key structures including the medial and lateral meniscal insertions, the posterior cruciate ligament, the Menisco-Femoral ligaments and a false Menisco-Femoral ligaments should all be identified separated by recesses of the joint.



ANTERIOR CRUCIATE
The anterior cruciate ligament (ACL) runs from a semicircular origin on the medial aspect of the lateral femoral condyle, in a spiral course forwards and laterally to a fan shaped insertion on the anterior tibial eminence.
It runs parallel to the intercondylar roof
It comprises two bundles, the largest is the anteromedial bundle anteromedial band becomes taut in flexion
The insertion can be ill defined as it fans out and blends with the ant horn of lateral meniscus
The AMB is low signal on most sequences the PLB is brighter and less well defined
Its neurovascular supply is from the lateral geniculate artery and tibial nerve branches
In children the lower third of the ligament in particular can be poorly defined. Indeed in very young children the anteromedial bundle in its entirety may be poorly demarcated making interpretation of anterior cruciate ligament rupture more difficult.

Fortunately, in children it is rarely injured and when it occurs it is most commonly an avulsion injury from the tibial insertion.

A synovial fold called the Ligamentum Mucosum runs parallel to the ACL and in front of it. A prominent fold may mimic the appearance of an intact ACL.

A minimum slice thickness of 4mm is recommended to ensure that the ligament is properly seen. Orientation of images along the axis of the ACL can be helpful, . Sagittal images are supported by coronal and axial sections. These can be particularly helpful in providing alternative visualisation of the femoral origin which can sometimes be difficult to depict on sagittal images.







DISCOID MENISCUS

Nearly all lateral
Body width more than 15mm
Coronal images best for assessment