Download Cystic and "cyst-like" lesions of the knee joint and around the knee

Cystic and "cyst-like" lesions of the knee joint and around
the knee : a pictorial essay in MR imaging
Poster No.:
C-2338
Congress:
ECR 2015
Type:
Educational Exhibit
Authors:
A. Plotas , I. Shaikh , K. Latief ; Nottingham/UK, Bedford/UK
Keywords:
Musculoskeletal system, Musculoskeletal joint, MR, Imaging
sequences, Education and training
DOI:
10.1594/ecr2015/C-2338
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Learning objectives
A cystic or a "cyst-like" lesion represents a common finding in a MRI examination of the
knee. They are ususally fluid-filled bursae, synovial cysts of the popliteal space, meniscal
cysts, ganglionic cysts or other fluid collections. The learning objective of this presentation
is the description of above abnormalities and make the radiologist familiar and confident
with their imaging features.
Background
The cystic lesions of the knee represent a common clinical problem. Histologically they
are divided in two types: ganlgia and synovial cysts (bursae). Ganglia are benign cystic
lesions lined by a dense fibrous capsule containing internal viscous material. Ganglia may
arise from joint capsules, ligaments, tendon sheaths, bursae or subchondral bone and
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generally do not communicate directly with the joint . Sometimes ganglia may undergo
process of synovialization. Synovial cysts are lined by synovial cells and ususally contain
viscous fluid. Bursae are located between surfaces, where there is friction and movement,
often between different tissues (ie tendon and bone). Bursae are seen in predictable
locations. Both ganglia and synovial cysts may undergo to haemorrhage. It is also
important to keep in our mind that synovial cysts (bursae) reveal all the potentional
pathologies of the synovium ( such as synovitis, PVNS, tumors).
The clinical presentation of a cystic lesion depends on its location, size and relation with
the surrounding structures.
Findings and procedure details
According to the location of a cystic or "cyst-like" lesion they can be categorised in
posterior, anterior, medial, lateral and other cystic lesions.
POSTERIOR KNEE
Popliteal or "Baker" cysts are seen in 10-41% of the knee and the prevalence increases
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with the age and the presence of arthritis or knee effusions They are located in the
medial gastrocnemius-semimembranosus bursa, which is composed by two parts, the
gasstrocnemius and the semimembranosus bursa, that maybe partially separated by a
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central septum (Fig.1). The typical location of a popliteal cyst is along the medial side of
the popliteal fossa. However, they can extend laterally, or superiorly depending on their
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size. We must have always in mind that more complex pathologies such as neoplastic
synovial lesions may arise in bursae locations (Fig. 2).
The popliteus bursa lies at the distal apect of the popliteous tendon sheath and can
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also communicate with the tibiofibular joint (Fig.3).
ANTERIOR KNEE
The suprapatellar bursa lies proximal to the knee joint capsule between the rectus
femoris tendon and femur. Communication of this bursa with the knee joint is found in
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approximately 84% of the adults .
The prepatellar bursa is located between the patella and the overlying subcutaneous sift
tissues. Inflammation of this bursa can occur as a result of overuse and maybe caused
by occupational kneeling or crawling. Prepattelalar bursitis maybe also a manifestation
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of gout . Other synovial disorders sush as PVNS may also affect this bursa (Fig.4).
The superficial infrapattelar bursa is located between the tibial tubercle and the
overlying skin. Direct trauma to this bursa may result in inflammatory and haemorrhagic
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bursitis. However, this not a common site of bursitis (Fig.5).
The deep infrapattelar bursa is located between the posterior margin of the distal part
of the patellar tendon and the anterior aspect of the tibia. A tiny amount of fluid is usually
seen in asymptomatic patients. We beleive this is a normal finding. Large collections in
this bursa ususally results form overuse of the knee extensor mechanism particullarly
in jumbers and runners and is manifested as anterior knee pain suggestive patellar
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tendonitis (Fig.6).
MEDIAL KNEE
The anserine bursa separates the pes anserinus, which is formed by the distal parts
of the tendons of the sartorius, gracilis and semidendinosus muscles, from the distal
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portion of the tibial collateral ligament and the bony sustface of the medial tibial condyle .
Anserine bursitis results from overuse, especially in runners and is manifested by medial
knee pain and swelling that may mimic medial meniscal tear or injury of the mediall
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collateral ligament . Its MR appearance is a fluid collection in the aforementioned location
(Fig.7). The differential diagnosis includes an atypical synovial cyst and a parameniscal
cyst, lesions that may also be found in this position.
The semimembranosus-tibial collateral ligament bursa (SM-TCL) is located posterior
and superior to the pes anserine bursa (Fig 8). The superficial part of this bursa lies
between the semimembranosus tendon and the medial collateral ligament and the deep
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part lies between the semimembranosus tendon and medial tibial condyle .Inflammation
of this bursa results in pain over the posteromedial aspect of the knee and may simulate
a meniscal abnormality.
The medial collateral ligament bursa is located between the superificial and deep
layers of the medial collateral ligament. Bursitis in this location causes medial joint pain
suggestive of injury of the medial meniscus ir medial collateral ligament. MR images show
a well-defined fluid collection between the deep and superficial portions of the medial
collateral ligament (Fig.9). Diffferentiation of bursal fluid from a parameniscal cyst can
sometimes be difficult, but most tears of the medial meniscus are seen posteromedially,
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and therefore, most parameniscal cysts occur posterior to the MCL .
LATERAL KNEE
The iliotibial bursa is located between the diastal part of the distal iliotibial parrt near
its insertion on Gerdy s tubercle and the adjacent tibial surface. It may mimic iliotibial
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tendinitis and lateral meniscal or lateral collateral ligamentous pathology . On MR
images iliotibial bursitis is demonstrated as a well-demarcated fluid collection between
the insertion of the distal iliotibial band and the adjacent bony surface (Fig.10 and 11).
OTHER CYSTIC LESIONS
Parameniscal cysts are formed by extrusion of joint fluid through a meniscal tear into
the adjacent tissues, indicating thus the presence of a meniscal tear. Parameniscal cysts
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are minifested by knee pain, locking, and a mass adjacent the joint . On MR images, they
appear as well-defined cysts located adjacent to a meniscal tear (Fig.12, 13).
Cysts of the proximal tibiofibular joint communicate with the knee joint in
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approximately 10% of the population . They can cause focal masses, apin or neuroapthy
due to compression on the common peroneal nerve if they arise on the pasterior aspect
of the tibiofibular joint. A cyst may also extend laterally around the fibular head, causing
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either a neural compression or an intraneural ganglion in the peroneal nerve . Large
proximal tibiofibular joint cysts may erode adjacent bone, similating a more aggressive
lesion (Fig.14, 15).
Ganglia around the knee joint can produce pain and swelling in the knee, but are usually
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asymptomatic .Ganglia have a predilection for periarticular locations, can be attached
to a joint capsule or tendon sheath and sometimes reveal connection with the synovial
cavity. Other possible locations of ganglia are within muscles, ligaments, tendons or
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nerves . On MR images, para-articular ganglia present as well-defined, rounded or
lobular lesions (Fig. 16, 17,18).
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Hoffa s fat pad ganglion is an intracapsular, extrasynovial structure in the anterior
aspect of the knee that lies below the patella, posterior to the patellar tendon and anterior
to the tibiofemoral articulation
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. Although the cause is not known, speculation includes
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trauma and transverse ligament degeneration . Hoffa s fat pad ganglia are typically
rounded hyperintense structures that may be unilocular or multilocular (Fig.19,20).
Mucoid degeneration and ganglia retated to the cruciate ligaments. Mucoid
degeneration of the cruciate ligaments is characterised by interstitial glycosaminoglycan
deposits between the normally aligned collagen bundles, resulting in a thickened ligament
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with intermediate signal intensity on T1W and diffuse increased on T2W images .
Mucoid degeneration is usually seen in middle-aged and elderly patients, but can also
occur in young people. Mucoid degeneration can be mistaken for a ligamenous tear on
MR imaging, but the diffuse nature and thickening of the ligament withot a history of
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trauma can aid in the diagnosis . Mucoid degeneration and gangion cysts of the cruciate
ligaments though to represent separate entities. Some authors have suggested there
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is a common pathogenesis . In MRI the ACL ganglia are interspersed within the ACL
fibres and it may extend towards the Hoffa s fat pad or posteriorly towards the femoral
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intercondylar fossa (Fig.21). PCL ganglia have a more typical appearance and resent
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as well-defined multilocular cysts adjacent and along the dosal PCL surface . (Fig.22).
Intraosseous gaglion cysts may arise at the site of insertion of the cruciate ligaments
or meniscotibial attachments and appear on MR images as small well-defined lesions
with minimal or no oedema in the adjacent marrow. They are usually asymptomatic and
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have been reported to occur in 1% of routine MR examinations of the knee .They are
manifested as sharply and well-demarcated homogenous fluid filled lesions, surrounded
by an oouter low-signal margin due to fibrous tissue (Fig.23).
Images for this section:
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Fig. 1: Axial PD fat sat : There is fluid filled medial gastrocnemius -semimembranosus
bursa divided by a thin septum.
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Fig. 2: Fig.2 Axial PD Fat Sat : There is a complex (solid and partially cystic) hyperintense
invasive mass in the medial aspect of the popliteal fossa that histologically was proven
as synovial sarcoma.
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Fig. 3: Coronal PD fat sat image shows a multilocular cystic lesion along the distal
popliteus tendon. It may be represents a ganglion cyst of the popliteus tendon or a fluid
filled popliteus bursa (there is no obvious communication with the tibiofibular joint).
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Fig. 4: The sagittal PD fat sat image shows a fluid-filled prepattelar bursa, which reveals
thickened dense septa and solid elements. PVNS was found after biopsy.
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Fig. 5: Sagittal PD fat sat image: There is a large fluid collection in the superificial
infrapattelar bursa.
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Fig. 6: Sagittal PD fat sat image: There is a trace of fluid in the deep infrapatellar bursa
(yellow arrow).
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Fig. 7: Fig.7 Axial PD fat sat image at the level of the tibia shows a fluid-filled anserine
bursa, located medially to the pes anserine tendons adjacent to the tibia.
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Fig. 8: Fig.8 Axial PD fat sat image at the level of medial femoral condyle. There is a
very small effusion in the SM-TCL bursa above the position of pes anserine bursa and
between the semimembranosus tendon and medial collateral ligament.
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Fig. 9: Fig.9 Cor PD Fs image shows a distended medial collateral bursa.
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Fig. 10: Fig.10: Coronal PD fat sat image shows a focal septated fluid collection (arrow)
between the iliotibial band and lateral femoral condyle.
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Fig. 11: Fig.11: The same patient as in Fig.10. Axial PD fat sat image shows a septated
fluid collection (arrow) in the iliotibial band bursa in a runner.
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Fig. 12: Fig.12: Sagittal PD fat sat image demonstrates a large cystic lesion in front of
the lateral meniscus, on a background of an horizontal tear in the anterior horn.
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Fig. 13: Fig. 13: The same patient as in Fig.12. There is a large septated lateral
parameniscal cyst., which lies anteriorly to the lateral meniscus.
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Fig. 14: Fig.14. Axial PD fat sat image shows a large anterior septated cyst in the proximal
tibiofibular joint, which erodes the fibular head.
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Fig. 15: Fig.15. The same patient as in Fig.14. The coronal STIR image shows a large
septated cyst of the proximal tibiofibular joint.
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Fig. 16: Fig 16. Axial PD fat sat image demonstrates a septated ganglionic cyst adjacent
to the pes anserine tendons at the level of the femoral metaphysis.
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Fig. 17: Fig.17: Axial PD fat sat image shows a ganglion cysts in front of the medial
patellofemoral ligament.
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Fig. 18: Fig.18: Coronal PD fat sat image reveal a lobulated-septated ganglionic cyst
adjacent to the popliteus tendon.
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Fig. 19: Fig.21 Sagittal PD fat image shows a large lobular ganglion cyst into Hoffa s
fat pad.
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Fig. 20: Fig 22. The same patient as in figure 21. Axial PD fat sat image. There a large
lobular and septated Hoffa s fat pad ganglion cyst posterior to the patellar tendon.
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Fig. 21: Fig.21 Sagittal PD fat sat image shows a small ganglion cyst embedded on the
posterolateral bundle of the ACL.
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Fig. 22: Fig.22. Coronal PD fat sat image demonstrates a lobular ganglion cyst embedded
in the PCL.
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Fig. 23: Fig.23. Axial PD fat sat image shows a small intraosseous ganglion cyst of the
tibia (arrow) adjacent to a small fluid-collection in the anserine bursa.
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Conclusion
Cysts and "cyst-like" lesions are a common finding inside and around the knee joint.
MRI can demonstrates excellent all these lesions. The radiologists must be familiar
about their appearances and differentiation, guiding thus specific treatment and avoiding
unwarranted interventional procedures.
Personal information
References
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