MR Imaging of the Infrapattelar Hoffa`s fat pad pathology

MR Imaging of the Infrapattelar Hoffa's fat pad pathology
Poster No.:
P-0045
Congress:
ESSR 2015
Type:
Educational Poster
Authors:
J. Araújo, S. Magalhães, I. Ferreira, J. Pires, R. Maia, M. Ribeiro;
porto/PT
Keywords:
Edema, Education, MR, Musculoskeletal soft tissue
DOI:
10.1594/essr2015/P-0045
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Learning objectives
The infrapatellar fat pad of the Hoffa is an intracapsular structure that is rountinely
visualized on the magnetic resonance images of the Knee. The purpose of this work is to
illustrate the most common imagiologic spectrum of Hoffa's fat pad pathology in Magnetic
Resonance imaging, with special focus on the intrinsic abnormalities.
Background
HOFFA´S FAT PAD ANATOMY (Fig.1)
•
The infrapatellar fat pad Hoffa is a structure located in the space between
the back side of the pattelar ligament and the real capsule.
•
It is routinely visualized on the magnetic resonance images of the knee.
•
There are other fat pads located between the sinovial and the joint capsule
of the knee joint that are intracapsular but extrasynovial structures.
•
Hoffa's fat lies behind the patella ligament and extends slightly superior and
posteriorly. It overlaps the inferior articular surface of the patella, the anterior
aspect of the femoral condyles, the intercondylar notch and the anterior
cruciate ligament.
•
The infrapatellar plica has a narrow femoral origin in the anterior part of
the interchondylar notch and widens as it descends anteriorly and inferiorly
throught the infrapatellar fat pad to attach distaly to the inferior pole of the
patella. (Fig.2)
•
Here are some aspects of the Hoffa's fat pad neurovascular supply:
- Vascular supply (superior and inferior genicular arteries) is related to the role played by
the synovium in the production of synovial fluid and removal of debris.
- The periphery is highly vascularised while more centrally, closer to the patellar ligament,
the blood vessels are less plentiful.
- It is inervated by branches of the femoral, common peroneal and saphenous nerves.
HOFF'S FAT PAD- symptomes and diagnosis.
•
Hoff's fat pad disease is characterized by knee pain, mostly under the
patella. Acute cases are generally post-traumatic. The clinical picture
Page 2 of 17
consists mainly of anterior pain and functional impairment, mimicking a
ligament injury.
•
At clinical examination, Hoffa's sign is difficult to observe but can be highly
specific. Extending a bent knee putting pressure on the patellar tendon
margins elicits a strong pain, an antalgic block and a defensive behavior of
the patient.
•
MRI clearly depicts Hoffa's infrapatellar fat pad and its findings may suggest
the frequently ignored diagnosis of Hoffa´s syndrome, alone or associated
with other local or systemic conditions.
•
Abnormalities within it most commonly are consequences of trauma and
degeneration, but inflammatory and neoplastic diseases of the synovium
can be confined to the fat pad. The commonest traumatic lesions follow
arthroscopy but intrinsic signal abnormalities can also be due to posterior
and superior impingment sydromes and following patellar dislocation.
Infrapatellar plica sydrome may also be traumatic in aetiology.
•
Abnormalities that are intrinsic to this fat pad include Hoffa disease,
intracapsular chondroma, infrapatellar plica sydrome, postarthroscopy
and postsurgery fibrosis and cyclop lesion. In addition, the infrapatellar
fat pad may be involved secondarily from extrinsic processes that include
articular disorders, such as joint effusion, synovial abnormalities, such as
pigmented vilonodular, lipoma arborescens, reumatoid, and extracapsular
abnormalities, such as Osgood-Schlatter disease, Jumper´s Knee and
Sinding-Larsen Johanssen syndrome.
Images for this section:
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Fig. 1: T1 FSE weighted image. Green: Hoffa´s fat pad
Page 4 of 17
Fig. 2: Sagital PD FAT-SAT imaging: Infrapatellar plica is thickned (arrow). There's also
a non specific nodular synovial thickening and fluid in the knee, specially in the suprapatellar recess.
Page 5 of 17
Imaging findings OR Procedure Details
Hoffa's disease (Fig.3 and 4)
•
Is a syndrome of infrapatellar fat pad impingement.
•
Sometimes after an acute impact or repetitive traumas, the fat pad can
become impinged (pinched) between the distal thigh bone, femoral condyle,
and the patella.
•
As the fat pad is one of the most sensitive structures in the knee, this
condition is known to be extremely painful
•
The resulting pain, swelling and fat hypertophy limits range of motion. Over
time, fibrotic tissue is formed.
•
Hoffa's impingment, specially in the supero-lateral aspect, is associated
with patellofemoral mechanical abnomalities, such as an increase in the
patellar tendon-patellar length ratio, increased lateral patellar tilt and a
shallower trochlear sulcus. These factors positively influence excessive
friction or pressure of the lateral patellar facet over the lateral femoral
condyle, resulting in edema in the intervening superolateral portion of Hoffa's
fat pad.
•
MR findings:
- Areas of increased signal intensity on T2-weighted MR images represent acute edema
and hemorrhage within the swollen fat.
- Bowing of the patellar tendon from mass effect is seen frequently
- A small joint effusion may be present.
- Subacute and chronic phases: fibrin and hemosiderin have low signal intensity
on both T1 and T2 weighted MR images. Fibrous tissue may be transformed into
fibrocartilaginous tissue, which rarely may ossify.
Intracapsular chondroma (Fig.5)
Page 6 of 17
•
Results from extrasynovial metaplasia in the capsule or adjacent connective
tissues.
•
Although it is a rare lesion, it overwhelmingly occur around the knee,
typically in the infrapatellar fat pad.
•
Sometimes may calcify and even ossify. It also may erode the lower pole of
the patella.
•
MR imaging demonstrates a heterogeneous mass within the infrapatellar
fat pad, with the high signal T2 intensity representing chondroid matrix or
edema and areas of low signal intensity, representing either calcification or
ossification.
Postsurgery/postarthroscopy fibrosis (Fig.6)
•
It is a complication like in the cyclop lesion, where an excessive scar tissue
response leads to painful restriction of joint motion, with scar tissue forming
within the joint and surrounding soft tissue.
•
Fibrous scarring after arthroscopic surgery can involve the infrapatellar fat
pad.
•
The arthroscopic portals are anterolateral, anteromedial and central.
•
Local fibrosis may cause apparent thickening of the patellar tendon, giving
the appearance of chronic tendinosis or jumper´s knee.
•
MR findings
- Predominantly low signal punctate, linear or even nodular areas on T1 and T2, coursing
from the posterior portion of the fat pad to the anterior surface of the tibia, wich can
cause impingment. There could also exist an heterogeneous signal on T2W images from
synovitis and granulation tissue intermingled with fibrous tissue.
Cyclops lesion (Fig.7)
•
It represents localized arthrofibrosis occurring after ACL reconstruction
(reaction to exposed ACL graft material or operative defris).
•
Consists in localized nodular soft-tissue mass that arises from the anterior
aspect of the ACL graft and extends anteriorly and superiorly in the
intercondylar region of the femur.
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•
MR findings:
- A focal nodular mass like lesion of low signal on T1W images and heterogeneous
signal on T2W images with/without cystic changes from synovitis and granulation tissue
intermingled with fibrous tissue.
Infrapatellar plica syndrome (Fig.8; Fig.2)
•
Is the most common plica in the knee. Is a pathological condition secondary
to inflamation.
•
Is easily identified at MR imaging as a linear low signal intensity structure
anterior and paralel to the ACL, on sagital images.
•
Because of its location and orietation, it is sometimes mistaken for the ACL.
It may also be mistaken for focal nodular synovites, post operative changes
or a loose body.
•
It represents an embryologic remmants of synovial fold and is originated
from the intercondylar notch in the region of the anterior cruciate ligament.
It widens into the anterior joint space and attaches into the synovial lining of
infrapatellar fat pad.
•
MR findings:
- there is a significant amount of curvilinear high T2 signal along the expected course
of the infrapatelar plica or markedly thickened plica is visualized. Thickening of the plica
even in the absence of edema or fluid suggests a chronic injury.
Pigmented Villonodular synovitis (PVNS)-(Fig.9)
•
Is a benign proliferative disorder of the synovium that may involve the
synovium of the joint, diffusely or focally, that may occur extraarticularly in
bursa (pigmented villonodular bursitis-PVNB) or tendon sheath (pigmented
villonodular tenosynovitis-PVNTS or cell tumor of the tendon sheathGCTTS).
•
GCTTS/PVNTS is the most common form of the disease.
•
Usually involves large joints as 80% of the cases affect the knee.
•
The masslike proliferative synovium could appear as an diffuse PVNS or a
limited single nodule in a focal form.
Page 8 of 17
•
Synovial deposition of hemosiderin results in irregular masses that show a
significant low signal on all sequences. Areas of high signal on T2 may be
present and are likely caused by inflamed synovium or joint effusion.
JUMPER KNEE-(Fig.10)
•
Jumper's Knee refers to a spectrum of disorders that occur in patients with
degeneration and/or tearing of the patellar tendon. It is one of the most
common tendon abnormalities in athletic active individuals, with special
incidence in basketball and volleyball players.
•
Patients with Jumper's Knee may experience a combination of proximal
patellar tendinopathy and osteochondral reactive marrow changes and Hoffa
edema.
•
MRI have high sensibility to diagnose this cases. T2 hyperintensity within
the proximal tendon is most commonly seen. More severe tendinopathy
demonstrates full thickness involvement by intrasubstance signal. Edema
may be present within the adjacent Hoffa's fat pad, with irregular T2
hyperintensity replacing normal fat signal. Partial thickness and complete
tears may also occur.
SINDING-LARSEN JOHANSSEN SYNDROME(Fig.11)
•
It represents a chronic traction injury of the immature osteotendinous
junction. Some authors classify it as a paediatric version of "jumper's knee".
•
It affects the proximal end of the patellar tendon as it inserts into the inferior
pole of the patella.
•
MRI shows abnormal signal in the inferior patella with irregular cortical
margins and osseous fragmentation
Images for this section:
Page 9 of 17
Fig. 3: Hoffa's disease. Sagittal DP FATSAT MR image showing edema and nodular
enlargement of the infrapatellar fat pad, with associated bowing of the patellar tendon.
Page 10 of 17
Fig. 4: PD Fat-Sat weighetd images on axial (A) and coronal (B) and T2 Fat-Sat weighted
MR image. Hoffa's superolateral impingement. Hyperintense edemalike signal (arrow)
within superolateral aspect of infrapatellar (Hoffa's) fat pad.
Fig. 5: Intracapsular chondroma. A and B - Sagittal and coronal T1-weighted SE MR
image - mass with mixed signal intensity within the infrapatellar fat pad. C - Sagittal
T2-weighted SE MR image shows high signal intensity within the mass that represents
edema and chondroid matrix (arrow). D - Axial T2* shows high signal intensity with central
areas of low signal intensity. E and F - Coronal e sagittal DP FATSAT SE MR image
shows high signal intensity lesion.
Page 11 of 17
Fig. 6: Arthrofibrosis. Pain and limitation in the knee extension in a patient with surgical
history of meniscal tear repair. Sagittal PD SE and T2 TSE FS MR imaging demonstrates
an heterogeneous nodular area with focal points of low signal, representing fibrosis
(arrows) in the posterior apex of the Hoffa's fat pad. There's also some fluid surrounded.
Fig. 7: Cyclops Lesion. A and B - Sagittal and axial PD tse fs MR image. C - T1-weighted
SE MR image. History of ACL repair - sequences show a lobular nodular area in the
posterior apex of Hoffa's fat pad, which presents with low signal on T1 and heterogeneus
signal on DP images. There is periferic high signal from synovitis and granulation tissue
and internal fibrous low signal tissue in the infrapatellar fat pad (arrows).
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Fig. 8: Sagittal fast spin-echo T2-weighted MR image with fat suppression through
intercondylar notch shows fluid signal along course of infrapatellar plica (arrows), which
was interpreted as injury to infra patellar plica. There´s also some high signal in the Hoffa
surround.
Page 13 of 17
Fig. 9: Localized intra-articular PVNS of the knee. Sagittal T2 FSE FS MR image.
Abnormal synovial tissue in the Hoffa's fat pad, which has low signal intensity due to
hemosiderin deposits (arrow).
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Fig. 10: A: Sagital T2 Fat-Sat weighted image; B axial DP Fat-Sat weighted image;
C: Sagital DP weighted image Focal hyperintensity involving the posterior thirds of the
proximal patellar tendon indicating a partial tear (arrows). There's also some bone marrow
edema in the patella and within the surrounding subcutaneous and infra-patellar Hoffa.
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Fig. 11: Sagital DP weighted image and T2 Fat-Sat weighted image Abnormal signal
in the inferior patella with irregular cortical margins and osseous fragmentation (arrow).
There's also some edema in the Hoffa.
Page 16 of 17
Conclusion
It is important to be familiar with the various pathologic entities that may occur in the
Hoffa's fat pad. MR is a very useful tool for the study of Hoffa's fat pad, whose local and
systematic involvement is an often ignored cause of anterior knee pain.
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•
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D.,RheeJ.RadioGraphics 2008;28:1493-1518
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Quadriceps Fat Pad Signal Intensity and Enlargement on MRI: Prevalence
and Associated Findings. Roth C., Jacobson J.; AJR 2004;182:1383-1387
•
Imaging of Intraarticular Masses. Sheldon P., Forrester D.; RadioGraphics
2005; 25:105-119
•
MRimaging of lipoma arborescens of the knee joint;Ryu,KN,Jaovisidha,
S.;AmericanJournalofRoentgenology,Vol 167, 1229-1232
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Boles.CA;Martin.DF; Synovial plica in the knee- AJR AMJ Roentgenol
2001:177:221-7
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Anatomy of theinfrapatellar fat pad . Swan, A., Mercer, S.; New ZealandJournal of Physiotherapy, March 2005, 33(1) 19-22.
Personal Information
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