Meniscal extrusion

Meniscal extrusion or subluxation refers to the peripheral meniscal margin extending beyond the external aspect of the tibiofemoral compartment of the knee.

Pathology

This can result from disruption of collagen fibers within the meniscus that provide hoop strength .

Associations

• medial meniscal extrusion is associated with osteoarthritis 
• meniscal tears: can occur with many tears, but especially root tears 
• meniscal maceration
• knee malalignment

Radiographic features

Meniscal extrusion can be assessed reliably on ultrasound and MRI  as well as on CT . Significant meniscal extrusion has been variably defined as ≥3 mm or ≥4 mm .