Meniscocapsular separation

Meniscocapsular separation refers to detachment of the meniscus from its capsular attachments. It is an uncommon injury.

Clinical presentation

Clinical findings are nonspecific and can include pain, instability, and joint effusion.

Pathology

Location

• it is more common in the medial (more frequently posterior horn region ⁵) than in the lateral compartment of the knee
  • ramp lesions are a specific type of meniscocapsular injury associated with ACL-deficient knees ⁶
• meniscofemoral detachment is more common than meniscotibial detachment ⁴

Associations

While it can uncommonly occur in isolation, it is more often associated with other ligamentous injuries.

Radiographic features

MRI

Meniscocapsular separation is usually diagnosed arthroscopically and the positive predictive value (PPV) of MRI has been traditionally described as being low ³ (as low as 9% medially and 13% laterally). 

Low predictive value MRI findings that have been correlated with meniscocapsular separation include ^1-2:

• interposition of fluid between the meniscus and the medial collateral ligament
• meniscal corner tears: according to one study had a PPV of 0% medially and 50% laterally ³
• perimeniscal fluid
• meniscofemoral and meniscotibial extension tears
• irregular meniscal outline
• increased distance between the meniscus and the medial collateral ligament
• visualization of fluid from the superior all the way to the inferior end of the meniscus has been described as a more suggestive feature ^{5 (PPV unknown)}

On MR arthrography meniscocapsular separations have been correlated with interposition of contrast medium between the meniscus and the medial collateral ligament.

Treatment and prognosis

It may heal after conservative treatment or after re-suturing the meniscus into the capsule.

Complications

Potential complications include:

• increased meniscal mobility and resultant meniscal tears ⁵

Differential diagnosis

On MRI consider a normal menisco-synovial recess / perimeniscal recess ⁴.