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MRI characteristics of cysts and "cyst-like" lesions in and around the knee: what the radiologist needs to know.

Perdikakis E, Skiadas V - Insights Imaging (2013)

Bottom Line: A variety of benign cystic or "cyst-like" lesions may be encountered during a routine magnetic resonance imaging (MRI) of the knee.In addition, normal anatomic bursae and recesses may be misdiagnosed as an intra-articular cystic lesion when they are distended.However, the majority of the aforementioned lesions have characteristic MR appearances that allow a confident diagnosis, thus obviating the need for additional imaging or interventional procedures.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, 412 General Military Hospital-212 Mobile Army Surgical Hospital, Terma Lefkou Pyrgou, Xanthi, 67100, Greece, perdikakis_ev@yahoo.gr.

ABSTRACT

Objectives and methods: A variety of benign cystic or "cyst-like" lesions may be encountered during a routine magnetic resonance imaging (MRI) of the knee. These lesions comprise a diverse group of entities from benign cysts to complications of underlying diseases. In addition, normal anatomic bursae and recesses may be misdiagnosed as an intra-articular cystic lesion when they are distended. However, the majority of the aforementioned lesions have characteristic MR appearances that allow a confident diagnosis, thus obviating the need for additional imaging or interventional procedures.

Results: This article includes a comprehensive pictorial essay of the characteristic MRI features of common and uncommon benign cysts and "cyst-like" lesions in and around the knee joint.

Discussion: For accurate assessment of the "cystic structure", a radiologist should be able to identify typical MRI patterns that contribute in establishing the correct diagnosis and thus guiding specific therapy and avoiding unwarranted interventional procedures such as biopsy or arthroscopy.

Teaching points: • Cystic lesions are common in knee MRI and the commonest, the Baker's cyst, has an incidence of 38 %. • Synovial cysts, meniscal cysts, normal knee bursae and recesses have characteristic MR appearances. • Miscellaneous "cyst-like" lesions may require a more dedicated MR protocol for a correct diagnosis.

No MeSH data available.


Related in: MedlinePlus

Popliteal cysts. The axial (a) and sagittal (b) fat saturated proton density weighted images show a large multiseptated popliteal cyst (asterisks) emerging between the medial gastrocnemius tendon (black arrow) and the semimembranosus tendon (white arrow) and abutting the medial gastrocnemial muscle belly (GN). The axial (c) fat saturated proton density weighted image shows a ruptured popliteal cyst (arrowheads). The axial (d) fat saturated proton density weighted image demonstrates a Baker’s cyst (white arrow) with a single loose osteocartilaginous body inside the cyst (black arrow)
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Fig1: Popliteal cysts. The axial (a) and sagittal (b) fat saturated proton density weighted images show a large multiseptated popliteal cyst (asterisks) emerging between the medial gastrocnemius tendon (black arrow) and the semimembranosus tendon (white arrow) and abutting the medial gastrocnemial muscle belly (GN). The axial (c) fat saturated proton density weighted image shows a ruptured popliteal cyst (arrowheads). The axial (d) fat saturated proton density weighted image demonstrates a Baker’s cyst (white arrow) with a single loose osteocartilaginous body inside the cyst (black arrow)

Mentions: The term popliteal cyst is a “misnomer” since it does not represent a true cyst, but actually corresponds to a fluid distension of the gastrocnemius-semimembranosus bursa, which occasionally communicates with the knee joint [6, 8]. Regarding its pathogenesis, a valvular mechanism between the knee joint and the bursa has been implicated, which allows joint fluid to communicate in a unidirectional mode. On MRI, they manifest as well defined unilocular or multilocular cystic masses, located posteromedially, arising between the tendon of the semimembranosus and the medial head of gastrocnemius [1, 2, 4–8]. Baker’s cyst can be effectively diagnosed with MRI since the fluid-distented gastrocnemius-semimembranosus bursa is easily depicted on T2-weighted MR images, especially in the axial plane. Fluid signal intensity is seen in all sequences in cases of popliteal cysts [8, 9]. Nevertheless, complications such as haemorrhage, rupture, the presence of intra-articular loose bodies and synovial proliferative reaction-diseases may produce a more heterogeneous appearance. Differential diagnosis from other cyst-like lesions and soft tissue tumours is thus imperative and requires a dedicated contrast-enhanced MRI examination protocol in the aforementioned cases [8–13]. Increased signal intensity within the cyst on T1-weighted images may appear in an infected or haemorrhagic cyst. The cyst may extend to any direction, but most commonly inferomedially. Lateral or intramuscular extension is observed relatively rare. A ruptured popliteal cyst is efficiently demonstrated as a high signal intensity oedema dispersing into the adjacent soft tissues and fascial planes on fat-suppressed T2-weighted sequences (Fig. 1).Fig. 1


MRI characteristics of cysts and "cyst-like" lesions in and around the knee: what the radiologist needs to know.

Perdikakis E, Skiadas V - Insights Imaging (2013)

Popliteal cysts. The axial (a) and sagittal (b) fat saturated proton density weighted images show a large multiseptated popliteal cyst (asterisks) emerging between the medial gastrocnemius tendon (black arrow) and the semimembranosus tendon (white arrow) and abutting the medial gastrocnemial muscle belly (GN). The axial (c) fat saturated proton density weighted image shows a ruptured popliteal cyst (arrowheads). The axial (d) fat saturated proton density weighted image demonstrates a Baker’s cyst (white arrow) with a single loose osteocartilaginous body inside the cyst (black arrow)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3675245&req=5

Fig1: Popliteal cysts. The axial (a) and sagittal (b) fat saturated proton density weighted images show a large multiseptated popliteal cyst (asterisks) emerging between the medial gastrocnemius tendon (black arrow) and the semimembranosus tendon (white arrow) and abutting the medial gastrocnemial muscle belly (GN). The axial (c) fat saturated proton density weighted image shows a ruptured popliteal cyst (arrowheads). The axial (d) fat saturated proton density weighted image demonstrates a Baker’s cyst (white arrow) with a single loose osteocartilaginous body inside the cyst (black arrow)
Mentions: The term popliteal cyst is a “misnomer” since it does not represent a true cyst, but actually corresponds to a fluid distension of the gastrocnemius-semimembranosus bursa, which occasionally communicates with the knee joint [6, 8]. Regarding its pathogenesis, a valvular mechanism between the knee joint and the bursa has been implicated, which allows joint fluid to communicate in a unidirectional mode. On MRI, they manifest as well defined unilocular or multilocular cystic masses, located posteromedially, arising between the tendon of the semimembranosus and the medial head of gastrocnemius [1, 2, 4–8]. Baker’s cyst can be effectively diagnosed with MRI since the fluid-distented gastrocnemius-semimembranosus bursa is easily depicted on T2-weighted MR images, especially in the axial plane. Fluid signal intensity is seen in all sequences in cases of popliteal cysts [8, 9]. Nevertheless, complications such as haemorrhage, rupture, the presence of intra-articular loose bodies and synovial proliferative reaction-diseases may produce a more heterogeneous appearance. Differential diagnosis from other cyst-like lesions and soft tissue tumours is thus imperative and requires a dedicated contrast-enhanced MRI examination protocol in the aforementioned cases [8–13]. Increased signal intensity within the cyst on T1-weighted images may appear in an infected or haemorrhagic cyst. The cyst may extend to any direction, but most commonly inferomedially. Lateral or intramuscular extension is observed relatively rare. A ruptured popliteal cyst is efficiently demonstrated as a high signal intensity oedema dispersing into the adjacent soft tissues and fascial planes on fat-suppressed T2-weighted sequences (Fig. 1).Fig. 1

Bottom Line: A variety of benign cystic or "cyst-like" lesions may be encountered during a routine magnetic resonance imaging (MRI) of the knee.In addition, normal anatomic bursae and recesses may be misdiagnosed as an intra-articular cystic lesion when they are distended.However, the majority of the aforementioned lesions have characteristic MR appearances that allow a confident diagnosis, thus obviating the need for additional imaging or interventional procedures.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, 412 General Military Hospital-212 Mobile Army Surgical Hospital, Terma Lefkou Pyrgou, Xanthi, 67100, Greece, perdikakis_ev@yahoo.gr.

ABSTRACT

Objectives and methods: A variety of benign cystic or "cyst-like" lesions may be encountered during a routine magnetic resonance imaging (MRI) of the knee. These lesions comprise a diverse group of entities from benign cysts to complications of underlying diseases. In addition, normal anatomic bursae and recesses may be misdiagnosed as an intra-articular cystic lesion when they are distended. However, the majority of the aforementioned lesions have characteristic MR appearances that allow a confident diagnosis, thus obviating the need for additional imaging or interventional procedures.

Results: This article includes a comprehensive pictorial essay of the characteristic MRI features of common and uncommon benign cysts and "cyst-like" lesions in and around the knee joint.

Discussion: For accurate assessment of the "cystic structure", a radiologist should be able to identify typical MRI patterns that contribute in establishing the correct diagnosis and thus guiding specific therapy and avoiding unwarranted interventional procedures such as biopsy or arthroscopy.

Teaching points: • Cystic lesions are common in knee MRI and the commonest, the Baker's cyst, has an incidence of 38 %. • Synovial cysts, meniscal cysts, normal knee bursae and recesses have characteristic MR appearances. • Miscellaneous "cyst-like" lesions may require a more dedicated MR protocol for a correct diagnosis.

No MeSH data available.


Related in: MedlinePlus