The medial meniscus is the most affected (23%) and 12% lateral meniscal lesions. It is a stereotyped traumatic lesion that starts from the meniscal periphery and cracks its longitudinal axis to the free edge. The anterior horn is never reached in isolation.
The sensitivity of MRI for lateral lesions is poor (57%).
MRI:
It appears vertical (relative to the plane of the tibial plateau) or oblique on the coronal and sagittal sections in hypersignal T2. It does not change direction .
It affects the posterior horn of the medial meniscus in the red zone (external third), vascularized, peripheral, meniscus, which explains the possibility of spontaneous repair in these young subjects.
Complication: bucket handle
Definition:
It is a post-traumatic longitudinal vertical fissure that starts backwards and continues forward. The meniscal fragment remains attached for a long time to the rest of the meniscus, before and after it, and then releases itself. The bucket handle mostly reaches the MM (5).
Clinic:
The meniscal fragment is luxurious in flexion in the notch explaining the master symptom of the bucket handle which is the blockage . The patient or surgeon can unblock the knee by flexing flexion maneuvers.
MRI:
Sagittal : sign of the “double posterior double cross”. The luxated fragment in the notch, bulky, appears in front of the LCP. The part of the bucket handle bent over the anterior horn gives a “megacorne anterior” or the double delta sign.
Loss of normal meniscal continuity (disappearance of the meniscal “butterfly”).
The residual MM is small and signal decreased.
Coronal : presence of a third element in the notch in hyposignal in addition to the LCA and the LCP. It is the free meniscal fragment. The residual meniscus appears “cut-away”, small.
Axial : a very useful plan for the analysis of the bucket handle because it is electively formed in this plane. The meniscal fragment appears sinuous in the notch and folded back on itself.
Meniscal Contusion:
Accompanying a bony contusion touches the posterior horn of the MM. It results in a non-linear hypersignal that should not be confused with a rupture.