Transcript Presentation3.ppt

Knee MRI
Fall 90
Anterior
Cruciate
Ligaments
(ACL)
In extension with the medial femoral
condyle removed depicts laxity of the
anteromedial bundle (red) and a taut
posterolateral band (blue).
In flexion, the anteromedial band
(red) becomes taut and the
posterolateral band (blue) becomes
lax.

Kissing anterior bone bruises
indicative of hyperextension
mechanism in a patient with an
ACL tear (ACL not shown).
Sagittal
T1-weighted
MRI
shows apposing ill-defined
hypointense bone contusions of
the anterior femur and adjacent
tibial plateau. T2-weighted
imaging is more sensitive than
T1-weighted
imaging
for
detecting acute bone bruises. A
small,
linear
incomplete
subchondral
fracture
is
superimposed on the tibial bone
bruise.

Prescribing
sagittal
images.
Images are obtained no more
than 10° oblique to a
perpendicular
to
a
line
connecting the posterior femoral
condyles (the bicondylar line).
Alignment of sections directly
along the long axis of the
anterior cruciate ligament (ACL)
in the axial plane is discouraged;
this will often lead to overly
oblique sagittal images with
degraded visualization of the
menisci
and
other
knee
structures.

Nonvisualization of the ACL
as a primary sign of a tear in
a T2-weighted sequence.
Sagittal T2-weighted fatsaturated fast spin-echo (FSE)
image shows replacement of
the ACL in the intercondylar
notch by extensive edemafluid signal intensity.

Posterior
cruciate
ligament
(PCL) tear in a patient with a
hyperextension-dislocation injury
and an anterior cruciate ligament
(ACL) tear. Sagittal T1-weighted
MRI shows an enlarged,
hypointense (obviously torn)
PCL (arrow).

(Same patient as in previous
image.) Acute hyperextensiondislocation tear of the ACL.
Sagittal T1-weighted image shows
ill-defined edema/hemorrhage in
the intercondylar notch in the
usual location of the ACL; no
normal ACL fibers are identified.
This is a common appearance of
an acute ACL tear on MRI
images. Some combination of
ACL, posterior cruciate ligament,
and lateral collateral ligament
tears are often present with
hyperextension-dislocation
injuries of the knee.

Contrecoup bone bruise of the
tibia in a patient with an ACL
tear. High-signal bone bruise in
the posteromedial aspect of the
tibial plateau (arrow). This is a
common finding in patients with
ACL tears secondary to a pivotshift/twisting mechanisms. This
bone bruise is a marker for a
pronounced twisting injury. As
such, meniscal tears are
exceptionally frequent. (Even
when no meniscal tears are seen,
occult medial meniscalmeniscocapsular junction tears
are not uncommonly present.)

Acute tear of the ACL manifest as
focal interruption of the ligament.
T2-weighted image shows focal
hyperintense edema and/or fluid
involving the proximal ACL.

Kissing anterior bone bruises
indicative
of
hyperextension
mechanism in a patient with an ACL
tear (ACL not shown). Sagittal T1weighted MRI shows apposing illdefined
hypointense
bone
contusions of the anterior femur and
adjacent tibial plateau. T2-weighted
imaging is more sensitive than T1weighted imaging for detecting acute
bone bruises. A small, linear
incomplete subchondral fracture is
superimposed on the tibial bone
bruise.

Posterior cruciate ligament
(PCL) tear in a patient with a
hyperextension-dislocation
injury and an anterior cruciate
ligament (ACL) tear. Sagittal
T1-weighted MRI shows an
enlarged,
hypointense
(obviously torn) PCL (arrow).

(Same patient as in previous image.)
Acute hyperextension-dislocation tear
of the ACL. Sagittal T1-weighted image
shows ill-defined edema/hemorrhage in
the intercondylar notch in the usual
location of the ACL; no normal ACL
fibers are identified. This is a common
appearance of an acute ACL tear on
MRI images. Some combination of
ACL, posterior cruciate ligament, and
lateral collateral ligament tears are often
present with hyperextension-dislocation
injuries of the knee.

(Same patient as in previous
image.) Fibular collateral ligament
tear in a patient with a
hyperextension-dislocation injury.
Coronal T1-weighted MRI shows
a torn, displaced fibular collateral
ligament (FCL) (arrow). The
fibular collateral ligament is a
major component of the lateral
collateral ligament complex.
Some combination of lateral
collateral
ligament,
anterior
cruciate ligament, and posterior
cruciate ligament tears are often
present
in
patients
with
hyperextension injuries to the
knee.

Pivot shift bone bruises of the
femur and tibia as a secondary
sign of an ACL tear. Sagittal T2weighted fast spin-echo fatsaturated MRI shows typical
pivot-shift subchondral bone
bruises of the posterior lateral
tibial plateau and lateral femoral
condyle near the anterior horn
meniscus. The probability of an
ACL tear is quite high if both
bone bruises are present, only
slightly lower if the tibial bone
bruise is present in isolation, and
only slightly lower still with an
isolated femoral bone bruise of
this appearance.

Pivot-shift osteochondral fracture
of the lateral femoral condyle. This
is a sagittal gradient-echo MRI in
17-year-old
boy
with
an
arthroscopically proven ACL tear.
The fracture is manifest by focal
cortical indentation of lateral
femoral condyle (arrow), near the
anterior horn lateral meniscus. This
fracture was accompanied by
typical femoral and tibial pivotshift bone bruises, as best
demonstrated on T2-weighted
sequences.

Contrecoup bone bruise of the
tibia in a patient with an ACL tear.
High-signal bone bruise in the
posteromedial aspect of the tibial
plateau (arrow). This is a common
finding in patients with ACL tears
secondary to a pivot-shift/twisting
mechanisms. This bone bruise is a
marker for a pronounced twisting
injury. As such, meniscal tears are
exceptionally frequent. (Even
when no meniscal tears are seen,
occult
medial
meniscalmeniscocapsular junction tears are
not uncommonly present.)

Prescribing sagittal images. Images
are obtained no more than 10°
oblique to a perpendicular to a line
connecting the posterior femoral
condyles (the bicondylar line).
Alignment of sections directly
along the long axis of the anterior
cruciate ligament (ACL) in the
axial plane is discouraged; this will
often lead to overly oblique
sagittal images with degraded
visualization of the menisci and
other knee structures.

Normal ACL in the sagittal plane.
Sagittal T1-weighted MRI shows a
ruler-straight hypointense ACL.
The normal ACL occasionally
demonstrates a mild smoothly
convex contour inferiorly, but
sharp angulation is abnormal.

Normal ACL in the coronal plane.
Coronal T1-weighted MRI shows
the lateral position of the ACL in
the intercondylar notch (arrow),
surrounded by high-signal fat.
Several hypointense ACL fascicles
diverge distally. Note that the
normal ACL often appears as
scant,
relatively
attenuated
fascicles on coronal MR images.

Normal ACL in the axial plane.
Axial fat-saturated neutral-weighted
fast spin-echo (FSE) MRI shows
the normal, linear hypointense
ACL adjacent to the lateral bony
wall of the upper intercondylar
notch (arrow). The normal ACL
moves away from the wall and
diverges into multiple fascicles on
more distal images.

Normal ACL in the sagittal plane.
Sagittal T1-weighted MRI shows a
ruler-straight hypointense ACL. The
normal
ACL
occasionally
demonstrates a mild smoothly
convex contour inferiorly, but sharp
angulation is abnormal.

Normal ACL in the coronal plane.
Coronal T1-weighted MRI shows
the lateral position of the ACL in
the intercondylar notch (arrow),
surrounded by high-signal fat.
Several hypointense ACL fascicles
diverge distally. Note that the
normal ACL often appears as
scant, relatively attenuated fascicles
on coronal MR images.

Normal ACL in the axial plane.
Axial
fat-saturated
neutralweighted fast spin-echo (FSE)
MRI shows the normal, linear
hypointense ACL adjacent to the
lateral bony wall of the upper
intercondylar notch (arrow). The
normal ACL moves away from the
wall and diverges into multiple
fascicles on more distal images.

Partial-volume inclusion of the
lateral femoral condyle causing a
false appearance of an ACL tear.
T1-weighted sagittal MRI shows an
ill-defined pseudomass about the
proximal ACL that could be taken
as evidence for ACL injury. With
evaluation of adjacent images and
other imaging planes, this should
not
cause
problems
in
interpretation.

Nonvisualization as a primary sign
of ACL tear. Complete (or nearcomplete) nonvisualization of the
ACL on sagittal images with illdefined edema and hemorrhage in
the usual location of the ACL is a
very common presentation of an
acute tear. Note: the normal ACL
is sometimes poorly seen on low–
echo-time (T1 or gradient echo)
sagittal images; this usually does
not present a problem in
interpretation if T2 images, and
images in other planes are carefully
correlated.

Nonvisualization of the
ACL as a primary sign of a
tear in a T2-weighted
sequence.
Sagittal
T2weighted fat-saturated fast
spin-echo (FSE) image
shows replacement of the
ACL in the intercondylar
notch by extensive edemafluid signal intensity.

Acute tear of the ACL manifest as
focal interruption of the ligament. T2weighted
image
shows
focal
hyperintense edema and/or fluid
involving the proximal ACL.

Primary signs of an ACL tear.
Sagittal
image
(top
left)
demonstrates
high-signal
disruption of the ACL with
multifragmented
appearance.
Coronal T2 (top right) and T1
(below)
images
show
nonvisualization of ACL fibers
and abnormal increased edema
and fluid in the lateral
intercondylar notch.

Abnormal flat axis of the ACL
as a primary sign of an ACL tear.
T1-weighted
sagittal
image
shows markedly flattened axis of
the distal ACL relative to the
intercondylar roof. This finding
has high specificity for an ACL
tear.

Pivot shift bone bruises of the
femur and tibia as a secondary
sign of an ACL tear. Sagittal T2weighted fast spin-echo fatsaturated MRI shows typical
pivot-shift subchondral bone
bruises of the posterior lateral
tibial plateau and lateral femoral
condyle near the anterior horn
meniscus. The probability of an
ACL tear is quite high if both
bone bruises are present, only
slightly lower if the tibial bone
bruise is present in isolation, and
only slightly lower still with an
isolated femoral bone bruise of
this appearance.

Pivot-shift
osteochondral
fracture of the lateral femoral
condyle. This is a sagittal
gradient-echo MRI in 17-year-old
boy with an arthroscopically
proven ACL tear. The fracture is
manifest by focal cortical
indentation of lateral femoral
condyle (arrow), near the anterior
horn lateral meniscus. This
fracture was accompanied by
typical femoral and tibial pivotshift bone bruises, as best
demonstrated on T2-weighted
sequences.

Contrecoup bone bruise of the
tibia in a patient with an ACL tear.
High-signal bone bruise in the
posteromedial aspect of the tibial
plateau (arrow). This is a common
finding in patients with ACL tears
secondary to a pivot-shift/twisting
mechanisms. This bone bruise is a
marker for a pronounced twisting
injury. As such, meniscal tears are
exceptionally frequent. (Even when
no meniscal tears are seen, occult
medial meniscal-meniscocapsular
junction tears are not uncommonly
present.)

Severe contrecoup bone bruise
of the posteromedial tibia with
associated impaction fracture.
Patient is a 26-year-old man
with an arthroscopically proven
ACL tear.

Anterior translation of tibia as a
secondary sign of an ACL tear.
Sagittal T1-weighted image in a
patient with an arthroscopically
proven ACL tear shows mild
anterior translation of the tibia. As
a result, a tangent line to the
posterior margin of the tibia passes
through the posterior horn lateral
meniscus (uncovered meniscus
sign). In normal knees, this line
passes posterior to the meniscus.
This sign should be sought on an
image through the midportion of
the lateral femoral condyle. Both
chronic and acute ACL tears often
demonstrate anterior translation of
the tibia.

Segond fracture in a patient with an ACL tear. T1 coronal image demonstrates
stereotypical elongate fracture fragment along the proximal and lateral margin
of the tibia (arrow). This fracture has a very high statistical association with
ACL tear. (Torn ACL is visualized in intercondylar notch.)

Segond fracture in a patient
with an ACL tear. Fat-saturated
proton-weighted fast spin echo
image shows stereotypical
elongate tibial fracture fragment
(arrow).
(Retracted,
discontinuous ACL fibers are
visible in the intercondylar
notch.)

Segond
fracture.
Anteroposterior (AP) knee
radiograph shows a linear
fracture
fragment
that
parallels the proximal lateral
surface of the tibia (arrow).
The probability of an ACL
tear is very high in patients
with a Segond fracture.

ACL insufficiency secondary to distal
tibial bony avulsion. An avulsion
fracture (arrow) is seen at the
expected region of the distal
insertion of the ACL near the tibial
spines. This finding should suggest
the possibility of ACL insufficiency/
injury because the ACL inserts just
lateral to the tibial spine. This form
of isolated injury (with or without
ACL compromise) is most common
in children. In adults, such fractures
imply a great force; the fractures are
often more extensive than expected
and are often accompanied by other
internal derangements.

Posterior cruciate ligament (PCL)
redundancy as a secondary sign of an
anterior cruciate ligament (ACL) tear.
T1-weighted sagittal MRI shows an
unusually arched PCL (arrow). This is
a relatively unreliable secondary sign
of ACL tear. Many patients with this
finding do not have an ACL tear and
some patients with an ACL tear do
not demonstrate a redundant PCL.
However, this patient did have an
arthroscopically proven ACL tear.

Kissing anterior bone bruises
indicative of hyperextension
mechanism in a patient with an
ACL tear (ACL not shown).
Sagittal T1-weighted MRI shows
apposing ill-defined hypointense
bone contusions of the anterior
femur and adjacent tibial plateau.
T2-weighted imaging is more
sensitive
than
T1-weighted
imaging for detecting acute bone
bruises.
A
small,
linear
incomplete subchondral fracture
is superimposed on the tibial
bone bruise.

Partial ACL tear. T2 sagittal image shows attenuated appearance of
ACL and question of subtle flattening of the axis of the ACL.

(Same patient as in the previous image.) Partial tear of the ACL.
Axial images show abnormally small, high-signal fragmentary
appearance of the ACL.

(Same patient as in the previous image.) Partial ACL tear. Sagittal T2-weighted
image shows typical ACL-tear related pivot-shift bone bruises of the lateral
femoral condyle and the posterolateral tibia. Patient had a normal Lachman
test. These images demonstrate that secondary signs of ACL tear (eg, pivotshift bone bruises) can occur with partial ACL tears and that high-grade
partial tears are difficult to distinguish from complete tears.

Partial tear of the ACL. T1weighted sagittal MRI image
shows disrupted ACL fibers
proximally compatible with
an ACL tear.

(Same patient as in previous image.)
Partial tear of the ACL. T1-weighted
sagittal MRI slice, immediately
adjacent to the previous image, shows
a normal-appearing ACL. Arthroscopy
confirmed a partial tear of the ACL.
Partial ACL tears may be suggested in
the proper clinical setting when
primary signs of ACL tear are present,
but at least one slice shows a normal,
taut-appearing ACL.

Chronic tear of the ACL with
empty notch sign. T1-weighted
coronal MRI shows only fat in the
lateral intercondylar notch; the
ACL is absent. A normal posterior
cruciate ligament (PCL) is present
in the medial aspect of the notch
(arrow). This is a frequent MRI
appearance of a chronic ACL tear
after the resolution of acute edema
and hemorrhage.

Chronic tear of the ACL
with
proximal,
focal
hyperintense
disruption.
Sagittal T2-weighted fast
spin-echo MRI shows focal
fluid-intensity interruption
of the proximal ACL
(arrow).
Absence
of
surrounding
edemalike
signal intensity is consistent
with the chronic nature of
the tear, as confirmed by
history and subsequent
endoscopy.

Chronic tear of the ACL, false-negative
result on MRI. The radiologist
interpreted this sagittal T2-weighted fast
spin-echo fat-saturated MRI, and other
images, as normal. In retrospect, the axis
of the ACL is abnormally horizontal
relative to the roof of the intercondylar
notch. Arthroscopy revealed a chronically
and grossly insufficient ACL with a few
fibers inserting on posterior cruciate
ligament (PCL). A chronically torn ACL,
with low-signal fibrous healing, can
appear misleadingly normal on MRI.

Chronic tear of the ACL, with
false-negative MRI report. The
proximal ACL appears slightly
attenuated; however, in the
absence of other primary or
secondary signs of tear, this
appearance lacks specificity for
an ACL tear. Images in other
planes appeared normal in this
patient; however, endoscopy
revealed a chronic incompetent
ACL.
This
case
again
demonstrates that chronic ACL
tears may present a challenge
to the MR-reader.

Mucoid degeneration or intraligamentous ganglion cyst of the ACL (unproven).
Patient had no history of trauma or instability. High-signal focal enlargement of the
proximal ACL is noted. The proximal splaying apart of fibers with "celery stalk"
appearance suggests mucoid degeneration; however, involvement of only the proximal
ACL is more typical of intraligamentous ganglion cyst. Before diagnosing either of
these entities, secondary MR signs of ACL tear should be excluded and the patient
should be confirmed as having a negative Lachman test result.

Ganglion cyst of the intercondylar
notch (unproven). Cystic focal signal
abnormality immediately posterior to
the proximal aspect of the ACL. The
fibers of the ACL proper appeared to
be uninvolved on all sequences. Fluidsignal ganglion cysts (vs synovial cysts
or joint recesses) are extremely
commonly
visualized
in
the
pericruciate regions on MR scans of
the knee.
Posterior
Cruciate
Ligaments
(PCL)
Anatomy

The PCL extends from the lateral surface of the medial femoral
condyle to the posterior aspect of the tibia. It is an intraarticular
but extrasynovial structure.

Two major components: Anterolateral & Posteromedial bundles

The meniscofemoral ligaments (Humphrey & Wrisberg) are
considered a part of the PCL complex.

Provides posterior knee stability.
PCL bundles with the knee in
flexion
depicts laxity of the
posteromedial bundle (blue) and
a taut anterolateral
The anterolateral bundle (red)
becomes lax and the posteromedial
bundle (blue) taut in extension.
The normal femoral origin of the posterior cruciate ligament is shown on this T1weighted coronal image. Only a portion of the ligament is seen because of the normal
oblique course of the ligament. The posterior cruciate ligament (black arrow) is of
lower signal intensity than the anterior cruciate ligament (open arrow).
Combined
anterior
and
posterior cruciate ligament
(PCL) tear. Proton-dense
sagittal image demonstrates
straightening
of
the
orientation of the course of
the PCL (straight black arrow
in A) resulting from the loss
of the normal restraining
function of the anterior
cruciate ligament secondary to
a severe tear. The protondense coronal view shows
almost all of the substance of
the PCL within one image (C),
reflecting
the
abnormal
accentuated
vertical
orientation of the ligament.
Proton-dense sagittal image (A) and T2-weighted
sagittal image (B) show an extensive tear involving the
proximal and distal portion of the PCL. The margins of
the PCL are well delineated indicating the ligament is
initial.
Anteroposterior
radiograph of the
right
knee
demonstrates
interruption
and
discontinuity
(black
arrow) at the femoral
origin of the posterior
cruciate
ligament,
representing
an
avulsion fracture.
Only a small portion of the posterior cruciate ligament
is seen on a coronal image. Increased signal intensity
within the posterior cruciate ligament on this proton
density image is the result of an interstitial tear.
Combined anterior and
posterior cruciate ligament
(PCL) tear. Proton-dense
sagittal image demonstrates
straightening
of
the
orientation of the course of
the PCL (straight black
arrow in A) resulting from
the loss of the normal
restraining function of the
anterior cruciate ligament
secondary to a severe tear.
The proton-dense coronal
view shows almost all of
the substance of the PCL
within one image (C),
reflecting the abnormal
accentuated
vertical
orientation of the ligament.
Proton-dense coronal image shows the relative intensity
of the anterior cruciate ligament (white arrow) and the
posterior cruciate ligament (black arrow). The posterior
cruciate ligament has less signal intensity because its
fibers are more linearly organized than the helically
arranged ACL.
Proton-dense sagittal images of the knee. The course of the normal
ligament of Humphrey is indicated (black arrow) as it progresses from
its origin at the posterior medial portion of the lateral meniscus (A), in
front of the lower portion of the posterior cruciate ligament (B), the
mid portion (C), and the proximal portion (D).
Proton-dense coronal images demonstrate the normal
ligament of Wrisberg originating from the medial horn of
the lateral meniscus and inserting at the lateral aspect of
the medial femoral condyle near the femoral origin of the
posterior cruciate ligament.
Anteroposterior radiograph of the
right
knee
demonstrates
interruption and discontinuity
(black arrow) at the femoral origin
of the posterior cruciate ligament,
representing an avulsion fracture.
The normal femoral origin of the posterior cruciate ligament is
shown on this T1-weighted coronal image. Only a portion of
the ligament is seen because of the normal oblique course of
the ligament. The posterior cruciate ligament (black arrow) is
of lower signal intensity than the anterior cruciate ligament
(open arrow).
Proton-dense sagittal image
shows the gentle convex
sloping course of the
normal posterior cruciate
ligament. Courtesy of Javier
Beltran, MD, Maimonides
Medical Center.
Proton-dense sagittal image demonstrates the normal
tibial insertion of the posterior cruciate ligament. The
insertion site is a vertically inclined structure posterior
to the articular surface.
Sagittal T2-weighted image shows
the normal femoral insertion of
the ligament of Wrisberg above
the insertion of the posterior
cruciate ligament.
Proton-dense sagittal image (A) and T2-weighted
sagittal image (B) show an extensive tear involving the
proximal and distal portion of the PCL. The margins
of the PCL are well delineated indicating the ligament is
initial.
Partial tear of the proximal PCL. The proton density
sagittal image (A) shows increased signal intensity in the
proximal portion of the PCL. This is clearly delineated
on the T2-weighted sagittal image (B).
Partial tear of the proximal femoral portion of the
PCL. The proton density sagittal image (A)
demonstrates increased signal intensity in the proximal
femoral portion of the PCL, confirmed on the T2weighted sagittal image (B). This is corroborated on the
proton density coronal image (C). Tears to the PCL
must be demonstrated on two different orientations.
Interstitial tear of the mid and distal PCL.
Proton density sagittal image (A), T2-weighted
sagittal image (B).
Proton-dense–weighted sagittal
image shows an extensive partial
tear of the mid substance of the
posterior cruciate ligament (large
black arrow). The uppermost
part of the ligament is intact on
the proton-dense images. Low
signal tendon is absent in the
region of injury, and replacement
by edema is seen. The normal
ligament of Humphrey (small
arrow) is visualized better
because it is adjacent to the high
signal intensity edema around the
torn posterior cruciate ligament.
A
sagittal
fat-saturated
proton density (sag FS PD)
image showing increased
signal, abnormal thickness,
and abnormal contour to the
tibial insertion site of the
PCL, indicating a partial
thickness tear. This is an
unusual site for tears because
the ligament is strongest
here. Avulsion injuries at this
site are more common.
Proton-dense sagittal (A) and coronal (B) images
demonstrate complete interruption of the proximal
portion of the posterior cruciate ligament.
Magic angle phenomenon. The T1-sagittal image (A)
demonstrates increased signal intensity at the apex of the
posterior cruciate ligament, which might indicate a tear. The
proton-dense–weighted image (B) demonstrates that region of
the ligament to be normal. Anatomic components oriented
approximately 55° to the main static magnetic field demonstrate
this phenomenon.
Proton-dense coronal images
demonstrate a bucket handle
tear of the medial meniscus
within the free fragment
displaced medially. This is
termed the double posterior
cruciate ligament sign and can
be confused with a posterior
cruciate ligament tear. Courtesy
of
Javier
Beltran,
MD,
Maimonides Medical Center.