Parameniscal Cyst

KEY FACTS

• Cystic mass in continuity with horizontal meniscal tear

Medial parameniscal cyst slightly more common than lateral parameniscal cyst
• Meniscal tear forces synovial fluid or mucoid content into parameniscal cyst
• Cyst is usually well defined and filled with anechoic or hypoechoic gelatinous-type fluid

Meniscal tear does not always have to be present

– Tear may have healed

Especially with anterior horn lateral meniscus
• Cyst may lie in direct continuity with meniscus or connect via serpiginous connecting stalk
• Colloid content of parameniscal cyst similar to that of ganglia and Baker cyst

Diagnosis of parameniscal cyst relies on showing continuity between cyst and meniscus
• Check for pericystic soft tissue inflammation
• Parameniscal cysts, especially medially, can be very large
• Comment on cyst size, loculation, extent, associated meniscal tear, recent cyst leakage ± localized inflammation

MR to assess meniscal tear

Intracapsular parameniscal cysts may not be visible on US
• US-guided aspiration ± hyaluronidase injection ± steroid injection

Provides temporary and often long-term symptom relief

– Especially for smaller cysts and poor surgical candidates

• Not every paraarticular cyst with pedicle extending to knee joint is parameniscal cyst

Need to distinguish from paraarticular ganglion
• Inflammation around parameniscal cyst usually results from recent leakage or extension

Leakage common cause of symptom exacerbation

• Cyst extending from meniscal tear

Usually horizontal tear (most common) or complex tear (2nd most common)

• T1WI

Hypointense cyst mass

If proteinaceous, cyst may be iso- or hyperintense
• T2WI

Rounded, hyperintense mass

– Lobulation and septation

Tear = linear hyperintense meniscal signal extending to articular surface

– Peripheral meniscal tear may not visibly connect with meniscal articular surface (noncommunicating tear)

• Parameniscal cyst ± extraarticular component with communicating stalk

Meniscal tear does not always have to be present, especially from anterior horn of lateral meniscus
• Meniscus is seen as diffusely echogenic, sharply defined structure within medial and lateral femorotibial compartments

Medial meniscus easier to see on US

– Only peripheral part of menisci can be seen on US

Body of menisci is best seen with limited views of other areas
• Meniscal tear = linear or wedge-shaped hypoechogenicity within meniscus extending to meniscal periphery

Be careful because normal meniscus can mimic appearances of horizontal tear

Extrusion of medial meniscal body is common accompanying feature

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Apr 9, 2020 | Posted by admin in MUSCULOSKELETAL IMAGING | Comments Off