Insertional cyst

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:

• zystische Veränderungen im Ansatzbereich der Rotatorenmanschette
• semimembranosus insertional cyst