Insertional cyst

MRI
characteristics of cysts and “cyst-like” lesions in and around the knee: what the radiologist needs to know. Semimembranosus insertional cyst. The coronal (a), sagittal (b) and axial (c) fat saturated proton density weighted images show an intraosseous cyst (white arrows) located at the semimembranosus insertion. Semimembranosus tendon is shown with a black arrow. Findings of ACL reconstruction are also visible
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Insertional cysts are usually well-defined, smooth-walled intraosseous cysts found at the insertion sites of tendon and ligaments.

Pathology

Etiology

They are thought to be a consequence of bone resorption due to chronic traction and avulsion stresses at the insertional sites of tendons and ligaments .

Location

In the knee, they can be found at the insertion sites of the semimembranosus tendon, the cruciate ligaments or meniscotibial ligaments .

Cysts commonly found in the greater and lesser tuberosity of the humeral head at the insertion sites of supraspinatus and subscapularis tendon could probably fall into the same category .

Radiographic features

Plain radiograph/CT

Plain radiographs or CT may show small, well-defined cysts.

MRI

MRI will show small, sharply demarcated and well-defined cystic lesions surrounded by a low signal .

  • T1: hypointense
  • T2: hyperintense
  • PDFS/T2FS: hyperintense

Surrounding bone marrow edema is very rare .

Differential diagnosis

Conditions which can mimic the presentation and/or the appearance of insertional cysts include :

  • intraosseous ganglion
  • degenerative subchondral cysts (geodes)
    • usually located at the opposing sides of the articular surfaces or weight-bearing regions
Siehe auch:
Assoziationen und Differentialdiagnosen zu Insertional cyst:
semimembranosus
insertional cyst
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