Download Understanding the "Dark Side" of the Knee

Understanding the “Dark Side” of the Knee: Imaging the Posterolateral Corner
Imaging the Injured PLC:
Magnetic Resonance
Imaging
Kirkland W. Davis, MD ; Jon A. Jacobson, MD ; Donna G. Blankenbaker, MD ; Ken L. Schreibman, MD, PhD ; Ben K. Graf, MD
1
2
1
1
3
(1) Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
(2) Department of Radiology, University of Michigan Medical School, Ann Arbor, Michigan
(3) Department of Orthopedics and Rehabilitation, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
ABSTRACT
Anatomy
Purpose:
Injuries of the structures of the posterolateral corner (PLC) of the knee
can have great significance. However, many radiologists have limited
knowledge of the anatomy and clinical significance of the PLC. This
poster will illuminate this poorly understood but important region.
Many authors divide the major structures of the PLC into dynamic
stabilizers and static stabilizers of the knee. The underlined structures
below are the classically described components of the PLC and are
demonstrated in accompanying figures.
Content Organization:
Topics reviewed in this poster will include:
• Clinical features of PLC injuries, including mechanisms of injury
and clinical relevance
• Anatomy of the major and minor structures of the PLC
• MR and ultrasound examples of the normal anatomy of the PLC
• MR examples of PLC injuries
• Examples of associated fractures visible on radiographs
• Surgical and conservative treatment options
Summary:
The viewer will
• Understand the significance of PLC injuries, including the increased
risk of failure of cruciate ligament reconstructions
• Know the gross, MR, and ultrasound anatomy of the PLC, including
the major (fibular collateral, biceps, popliteus, gastrocnemius,
popliteofibular, and capsule) and minor (fabellofibular and arcuate
ligaments) components of the PLC
• Recognize major injuries of the PLC
• Be familiar with current treatment options for PLC injuries
INTRODUCTION
The posterolateral corner (PLC) of the knee has been called the “Dark
side of the knee,” because of the difficulty in diagnosing injuries in
this region. There are several important structures that comprise the
PLC, and their injury can be important, whether these injuries occur
in isolation or with other internal derangement of the knee. However,
many radiologists have a limited understanding of the anatomy of this
region and the imaging appearance of the normal and injured PLC. This
presentation will review the anatomy of the PLC, clinical importance of
injuries there, imaging of the normal and injured PLC, and treatment of
PLC injuries.
Figure 1a: Popliteus;
Popliteofibular Ligament
The popliteus muscle belly
(triangular) and tendon are
depicted in orange, with the
tendon extending up to insert
on the lateral femoral condyle,
just inferior to the origin of
the fibular collateral ligament.
The popliteofibular ligament is
depicted in brown, curving down
to insert on the fibular styloid
just medial to the conjoined
tendon insertion.
• Dynamic stabilizers:
ÌÌ Popliteus muscle-tendon unit (see Figs. 1a, 2): constant
àà Originates from posteromedial tibia
àà Tendon passes through the popliteal hiatus of the posterior
horn lateral meniscus
àà Inserts onto sulcus on lateral surface of lateral femoral
condyle
ÌÌ Biceps femoris tendon (see Figs. 1b, 3): quite variable anatomy,
but overall constantly present
àà Long head joins conjoined tendon (both anterior and direct
arms)
àà Short head:
ww Direct arm also joins the conjoined tendon
ww Anterior arm inserts on superolateral tibia
ÌÌ Lateral head of gastrocnemius muscle (see Figs. 1c, 4): constant
àà Originates at supracondylar tubercle of distal femur
àà Closely applied to joint capsule at PLC
• Static stabilizers:
ÌÌ Lateral collateral ligament (fibular collateral ligament—FCL;
see Figs. 1b, 5): constant
àà Originates on lateral margin of lateral femoral condyle
àà Runs superficial to popliteus tendon
àà Blends with biceps tendon conjoined tendon
àà Inserts on lateral fibular head (occasionally with second limb
inserting on tibia)
ÌÌ Popliteofibular ligament (PFL; see Fig. 1a, 6): variably present
(38-100%, depending on the surgical series, but most authors
state it is essentially always present)
àà Arises from popliteus tendon
àà Inserts medial edge of fibula
àà Also called the fibular origin of the popliteus muscle
àà Stabilizes external rotation
ÌÌ Fabellofibular ligament (FFL; see Figs. 1d, 7): variably present
(20-87%)
àà Originates at fabella or lateral margin of gastrocnemius
àà Inserts on fibular styloid
àà Thickening of distal edge of capsular arm of short head of
biceps
ÌÌ Arcuate ligament (AL; see Figs. 1e, 8): variably present
(13-100%)
àà Inserts on fibular styloid
àà Triangular sheet of fibers
àà Lateral limb attaches to post capsule/femur
àà Medial limb blends with oblique popliteal ligament/capsule
àà Important stabilizer of PLC
ÌÌ Lateral capsular ligament (“mid-third” lateral capsular ligament)
ÌÌ Posterolateral capsule
• Popliteomeniscal fascicles
• Posterior horn lateral meniscus
• Lateral coronary ligament
• Iliotibial band (included in PLC by some authors)
Figure 1d:
Fabellofibular
Ligament
When a fabella is present,
the fabellofibular ligament,
depicted in green, originates
on the fabella and inserts
on the fibular styloid
near the insertion of the
popliteofibular ligament.
When no fabella is present,
the ligament may still exist;
the origin in this instance
would be the lateral margin
of the gastrocnemius
muscle/tendon.
Figure 1b: Biceps
Femoris; Fibular
Collateral Ligament
The biceps femoris muscle belly
(proximal) and tendon are depicted
in yellow, with the tendon
inserting on the fibular head as
part of the conjoined tendon,
just lateral to the fibular styloid.
The fibular collateral ligament,
depicted in pink, originates on the
lateral femoral condyle above the
popliteus insertion and forms the
other half of the conjoined tendon.
Figure 1c: Lateral
Head of the
Gastrocnemius
The lateral head of the
gastrocnemius muscle
belly (distal) and
tendon are depicted in
blue. The origin is the
supracondylar turbercle
of the distal femur. The
fabella, when present,
is a sesamoid within
the musculotedinous
junction.
Figure 2: Normal popliteus tendon
Figure 5: Normal Fibular Collateral Ligament
Fat-suppressed proton density coronal images demonstrate the normal
popliteus muscle and tendon (ellipse, image (a)), tendon passing
through the popliteal hiatus (arrow, image (b)), and tendon inserting
on the lateral femoral condyle (arrow, image (c)) deep to the fibular
collateral ligament. Sagittal proton density images show the popliteus
muscle posterior to the lateral tibia (bracket, image (d)) and tendon
passing through the popliteal hiatus (arrow, image (e)). Longitudinal
grayscale ultrasound demonstrates a normal fibrillar architecture of
the popliteus tendon in its mid portion (f) and distally (g). The left
arrow on image (f) denotes loss of echoes due to anisotropy.
(a) Coronal T1 image shows normal fibular collateral ligament (bracket)
originating from the lateral femoral condyle above the popliteus groove
and inserting onto the lateral
aspect of the fibular head. With
the biceps tendon, the FCL forms
the conjoined tendon at their
insertion. Longitudinal grayscale
ultrasound images show normal
(b) proximal and (c) distal fibular
collateral ligament (arrows)
originating from the lateral femoral
condyle above the popliteus
groove and inserting onto the
lateral aspect of the fibular head.
On image (b), note the intact
popliteus insertion deep to the
FCL.
All structures from figures
a-e combined in appropriate
layers.
(a, b) Sagittal proton density images demonstrate a normal arcuate
ligament (arrows) extending from the from the fibular styloid superiorly
along the posterior joint capsule. (c) Sagittal fat-suppressed T2 image
in the same patient demonstrates no edema posterior to the capsule in
the vicinity of the popliteal hiatus; when edema is present at that site,
consider arcuate ligament tear. (d) Coronal T1 image demonstrates
both limbs of the arcuate ligament (arrows). This ligament is seldom
discernible on MRI.
• Isolated injuries of PLC uncommon, but do occur (1/3-1/6 of all
PLC injuries said to be isolated).
• Mechanisms:
ÌÌ Blow to anteromedial knee
àà First injures arcuate ligament complex
àà With further rotation  PCL injured
ÌÌ Hyperextension with or without contact
ÌÌ Noncontact varus injury
• Typically high-energy injuries, especially in football, soccer, motor
vehicle vs. pedestrians, falls
• PLC injuries commonly accompanied by ACL or PCL injuries
• 10-15% have common peroneal nerve injuries.
• Popliteus injuries have a high association with ACL tears.
Imaging the Injured PLC:
Radiographs
• Usually normal
• Lateral joint space widening
• Fractures are uncommonly seen, but can be important clues:
ÌÌ Fibular head avulsion fracture = “arcuate fracture/sign” (see Fig.
9)
àà Small avulsion of styloid or medial fibular edema  arcuate
or popliteofibular ligament injury
àà Larger avulsion or diffuse edema  FCL/biceps injury
àà Highly associated with PCL ruptures
ÌÌ Avulsion of Gerdy’s tubercle
ÌÌ Segond fracture (see Fig. 10)
àà > 90% associated with ACL rupture
àà Also can be sign of PLC injury
ÌÌ Fracture of the anteromedial tibial rim (see Fig. 11)
• Varus stress view  wide joint space laterally (see Fig. 12)
Coronal fat-suppressed proton density images demonstrate disruption
of some of the fibers of the biceps (red arrow, image (a)), while others
remain intact (arrow, image (b)), indicating partial tear. However, there is
a complete tear of the fibular collateral ligament (blue arrow).
15a
2a
FEM
2b
TIB
5b
8b
5c
Figure 6: Normal Popliteofibular Ligament
(a) Coronal fat-suppressed proton density image demonstrates a normal
popliteofibular ligament (arrow) extending from the from the popliteus
musculotendinous junction and inserting onto the fibular styloid.
(b) Sagittal fat-suppressed T2 image demonstrates the popliteofibular
ligament near its insertion (arrow).
(c) Coronal T1 image in a different patient depicts the popliteofibular
ligament inserting on the fibular styloid (arrow).
(d) Longitudinal grayscale ultrasound image demonstrates a normal
popliteofibular ligament (arrows) extending from the from the popliteus
musculotendinous junction and inserting onto the fibular styloid.
2d
2c
LCL
8d
8c
TIB
Physical Exam
Figure 9: Arcuate Sign
• Especially in the acute setting, physical examination of the knee
can be difficult and discerning all elements of instability is a
challenge, even for skilled examiners.
• Posterolateral instability may be misperceived as PCL instability
alone.
• Specific tests:
ÌÌ Dial test (tibial external rotation): prone  increased external
rotation at 30° but not 90°  isolated injury of PLC; increased
external rotation at both angles  both PLC and PCL injuries.
Side-to-side difference of 10° or more suggestive of injury.
ÌÌ Posterolateral drawer test
ÌÌ Varus stress test at 0° and 30°
ÌÌ Reverse pivot shift
ÌÌ Assessment for varus thrust gait
ÌÌ External rotation recurvatum test
The structures of the PLC can also be discussed relative to their layers
as follows:
2e
6a
6b
TIB
2g
FIB
Figure 3: Normal Biceps Femoris Tendon
3a
POP
6c
Figure 16: Normal PFL
• Superficial layer (I):
ÌÌ Iliotibial band
ÌÌ Biceps tendon
• Middle layer (II):
ÌÌ Retinaculum, patellofemoral ligament
• Deep layer:
ÌÌ Fibular collateral ligament
ÌÌ Popliteus tendon
ÌÌ Popliteofibular ligament
ÌÌ Arcuate ligament
ÌÌ Fabellofibular ligament
Figure 13:
Imaging the PLC
3b
Clinical Significance
7a
7b
7c
• The elements of the posterolateral corner function to:
ÌÌ Prevent posterior translation of the tibia
ÌÌ Prevent varus angulation of the knee
ÌÌ Prevent external rotation of the tibia
• In the setting of a cruciate ligament reconstruction, leaving
posterolateral corner injuries untreated risks failure of the cruciate
procedure.
ÌÌ Anterior cruciate ligament (ACL) grafts rupture.
ÌÌ Posterior cruciate ligament (PCL) grafts become lax.
• FCL and deep ligament complex primarily responsible for
preventing varus and external rotation of the tibia.
• Posterolateral injuries may lead to posterolateral rotatory instability
and gait abnormalities, even without the usual concomitant injuries
to the cruciates and menisci.
• When overlooked, PLC injuries may cause chronic instability and
pain; osteoarthrosis may be the final result.
• Early repair of torn PLC structures improves outcomes (see below).
• Must have high index of suspicion clinically and radiologically
26b
Figure 22: Fibular Collateral Ligament Tear
Longitudinal grayscale ultrasound of the FCL demonstrates a normal
fibrillar pattern in the distal fibers (arrow) but a focal disruption
at its origin (ellipse) at the lateral femur, indicated by focal
hypoechogenicity.
Longitudinal grayscale ultrasound demonstrates no recognizable FCL,
biceps tendon, or PFL. Instead, there is only an irregular hypoechoic
region replacing them. The adjacent hyperechoic structures near the
bones may be shredded ligament fibers.
Figure 17: PLC Edema
Suggests Injury
Some authors recommend
performing a coronal oblique
proton density sequence, with
images angled to parallel the
popliteus tendon as it passes
through the hiatus, as depicted
by the red lines on the scout
sagittal proton density image.
However, most centers do
not add this sequence to their
routine knee MRI protocols.
17a
(a) Axial fat-suppressed T2 image
depicts the extensive edema
surrounding the PLC (bracket),
indicative of a significant injury
to the region. (b) Fat-suppressed
sagittal T2 image depicts a high
grade tear of the gastrocnemius
(arrow), while the coronal fatsuppressed proton density image (c)
depicts complete tears of the FCL
and popliteus tendon (arrows).
Figure 10: Segond Fracture
(a) AP radiograph demonstrates the classic Segond fracture (arrow).
This is an avulsion of the lateral tibial rim at the attachment of the
lateral capsular ligament. While these fractures are highly associated
with anterior cruciate ligament ruptures and meniscal tears, injuries
of the PLC are also common with this fracture. (b) Lateral radiograph
shows a large effusion (arrow) in this patient with significant internal
derangement. (c) Coronal fat-suppressed proton density image confirms
the Segond fracture (arrow). (d) Sagittal fat-suppressed T2 image confirms
the expected ACL rupture (arrow), with loss of continuity of fibers
proximally, abnormal orientation of distal fibers, and extensive edema.
(e) Coronal fat-suppressed proton density image shows the stump of
the ruptured popliteus tendon (red arrow) and the wavy, torn fibular
collateral ligament (blue arrow). (f) Coronal fat-suppressed proton density
image depicts the torn popliteofibular ligament (arrow).
9b
9c
Figure 11: Anteromedial Tibial Fracture
(a) Lateral radiograph of the knee demonstrates fragments from an
anteromedial tibial rim fracture (arrow) in this patient with multiple
injuries including PLC injury. (b) Fat-suppressed axial T2 MR image
shows the anteromedial tibial rim fracture (red arrow) and significant
edema surrounding the posterolateral corner (blue arrow). (Images
courtesy of D. Lee Bennett, MD, Iowa City, IA)
(a) Sagittal fat-suppressed T2 image demonstrates ACL rupture
(arrow), with the fibers following an abnormal course. (b) On
the sagittal proton density image, there is a horizontal tear of
the medial meniscus (arrow). (c) Coronal fat-suppressed proton
density image demonstrates edema surrounding an otherwise
intact popliteofibular
ligament (arrow). Sagittal
fat-suppressed T2 images
demonstrate partial
disruption of the popliteus
muscle belly (arrow, image
(d)) indicating a partial tear;
and edema in the expected
vicinity of the arcuate
ligament (arrow, image (e)),
suggesting injury to that
structure.
17b
Femur
FIB
Conclusion: Key Points
17c
Figure 20: Fabellofibular Ligament Tear
Figure 18: Arcuate Ligament Injury
Fat-suppressed (a) sagittal and (b) axial T2 images in a patient with a
flipped torn meniscus demonstrate prominent focal edema posterior to
the joint capsule in the vicinity of the popliteal hiatus, which suggests
arcuate ligament tear (arrows).
11b
11a
14b
Severe knee injury. (a) Fat-suppressed sagittal T2 image demonstrates
complete disruption of the fabellofibular ligament (arrow).
(b) Fat-suppressed coronal proton density image demonstrates
numerous injuries, including a high grade tear of the popliteus at its
femoral attachment (arrow).
Recommended articles in bold
18b
(a) Fat-suppressed sagittal T2 image shows edema within and
disorganization of ACL fibers (arrow), indicating rupture.
(b) Fat-suppressed coronal proton density image shows complete
disruption of the biceps tendon and FCL (ellipse).
(a) AP radiograph of the knee performed without stress shows a
wide lateral joint space (arrow).
(b) Coronal fat-suppressed proton density image depicts severe
disruption of the posterolateral corner (ellipse).
Fat-suppressed coronal proton density images of multiple injuries of the
posterolateral corner. There is a complete rupture of the FCL (red arrow)
and a partial rupture of the biceps (blue arrow, image (a)), and a high grade
partial tear of the popliteofibular ligament (arrow, image (b)), indicated by
swelling and increased signal but not complete disruption of fibers.
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25b
10d
14d
14e
19a
10e
10f
25a
Figure 21: Complex PLC Injury
Figure 19: ACL Rupture and PLC Injury
10c
20a
20b
14c
Figure 12: Lateral Joint Widening
• Anterior medial tibial rim fractures should focus attention on the
posterolateral corner.
• Segond fractures and avulsions of the fibular head should also
prompt a search for PLC injuries, as well as cruciate ligament tears.
• Tears of the popliteus muscle-tendon unit are usually associated
with tears of the anterior cruciate ligament.
• Don’t overcall edema along the FCL. As with the MCL, edema by
itself is common about the FCL with various knee abnormalities
and is not diagnostic of a sprain.
Longitudinal grayscale ultrasound (a) without stress and (b) with
valgus stress demonstrate no recognizable FCL or popliteus. With
valgus stress, the gap between the femur (“F”) and tibia (“T”) increases
prominently, indicating instability of the posterolateral corner.
m = meniscus.
Selected References
18a
10b
• Injury of the major structures of the PLC should be evident at MRI
and ultrasound.
• Individual assessment of the popliteofibular, fabellofibular,
and arcuate ligaments is not always possible; nevertheless,
abnormalities of these structures should be sought.
• Physical exam, surgical findings, and clinical outcome will be
the final determinants of the significance of radiologic findings
suggesting PLC injury.
• In the absence of other diagnoses, the patient with an injured
knee who has edema about the posterolateral corner should raise
suspicion of a PLC injury—this should be suggested to the referring
clinician.
• Focal edema at/posterior to the capsule just behind the region of
the popliteal hiatus may be due to a tear of the arcuate ligament.
Figure 25: PLC Instability
14a
10a
26d
26c
TIB
6d
(a, b) Coronal fat-suppressed
proton density images demonstrate
a normal fabellofibular ligament
(arrows) extending from the from
the fabella to the fibular styloid.
(c) Coronal T1 image in a different
patient depicts the fabellofibular
ligament inserting on the fibular
styloid (arrow).
(a) AP radiograph of a recently dislocated knee with PLC injury in
addition to other ligament injuries shows an anteromedial tibial rim
fracture (arrow) and lateral joint space widening.
(b) Coronal fat-suppressed proton density MR image confirms complete
disruption of the posterolateral corner.
(c) Lateral and (d) AP views of the knee after reconstruction of the fibular
collateral ligament and popliteus tendon with an Achilles allograft. Note
tunnels in both the femur and tibia as well as suture anchors and screw
with washer for reattachment.
26a
Coronal T1 image demonstrates
the normal popliteofibular
ligament curving down from
the popliteus musculotendinous
junction to insert on the fibular
styloid (arrow).
Figure 7: Normal
Fabellofibular Ligament
Sagittal proton density images demonstrate the origin of the lateral head
of the gastrocnemius muscle (arrows). The medial portion of the origin (a)
typically is more muscular, and the lateral aspect (b) is more tendinous.
4b
FIB
Figure 14: Complex Injury Including PLC
TIB
Figure 4: Normal Gastrocnemius
4a
(a) AP radiograph demonstrates a minimally displaced fracture of the
fibular head, sometimes referred to as the arcuate sign. This is somewhat
of a misnomer, as the fracture is more often associated with avulsion of
the attachment of the conjoined
tendon and less commonly the
arcuate ligament attachment.
(b, c) Coronal fat-suppressed
proton density images confirm
the fracture at the insertion of the
conjoined tendon, indicating this
to be a significant posterolateral
corner injury. There is extensive
surrounding edema. The
popliteofibular ligament also
is involved (arrow) and if this
patient has an arcuate ligament
it would also be attached to the
avulsed fragment.
Anatomy: Layers
TIB
Longitudinal grayscale ultrasound demonstrates ill-defined, swollen,
hypoechoic torn FCL and popliteus proximally (ellipse). Red arrow
demarcates a markedly hypoechoic and irregular, torn proximal
popliteofibular ligament, with the blue arrow demonstrating this
structure to be more normal distally near its insertion on the fibula.
9a
2f
FIB
Figure 23: Popliteofibular Ligament Tear
• Nonoperative: poor results in patients with grade 3 injuries
(complete tears) of the major structures
• Operative:
ÌÌ Improved results if perform in first 3 weeks; after this, scar tissue
develops, peroneal nerve injuries are more likely
ÌÌ Fix cruciate injuries first.
ÌÌ Direct repair of PLC structures with suture or suture anchors; or
grafting with hamstring tendons, biceps tendon, iliotibial band,
or allograft (see Fig. 26)
ÌÌ Chronic injuries: controversial as to best approach
àà Anatomic reconstruction
àà Stabilizing (tightening) procedures—e.g. sling procedure
àà Valgus tibial osteotomy may help as a start, unloading the
PLC.
ÌÌ Arthroscopy will not see the FCL, fabellofibular, arcuate, and
popliteofibular ligaments, which are extracapsular.
àà Clinical and radiological signs of PLC injuries needed to
direct open repair.
• Critical structures to repair are the FCL, popliteus tendon, and
popliteofibular ligament.
Figure 26: PLC Repair
Figure 24: Complex Ligament Tear
FEM
(a) Coronal T1 image shows normal biceps femoris tendon (bracket) at its
insertion on the fibula, lateral to the fibular styloid. The biceps inserts in
concert with the fibular collateral ligament as the conjoined tendon.
(b) Longitudinal grayscale ultrasound image shows normal biceps femoris
tendon (arrows) extending to its insertion on the fibula (FIB), lateral to the
fibular styloid.
• Normal tendons and ligaments demonstrate a fibrillar, hyperechoic
architecture.
• Tendon and ligament injuries can be demonstrated with ultrasound
(see Figs. 22-24):
ÌÌ Strains and sprains may demonstrate hypoechoic fluid
surrounding the tendon/ligament or focal hypoechoic areas
within the structure.
ÌÌ Partial tears demonstrate disruption of a portion of the fibers.
ÌÌ Complete tears demonstrate loss of continuity of all fibers of the
tendon or ligament.
• Ultrasound allows the potential for showing dynamic gapping if
stress is placed across the tendon/ligament (see Fig. 25).
• These techniques require experience with musculoskeletal
ultrasound and confidence in the anatomy.
Treatment
TIB
POP
8a
Imaging the Injured PLC: Ultrasound
15b
FIB
Arcuate Ligament
Figure 1f
Figure 8: Normal Arcuate Ligament
5a
Figure 1e:
The arcuate ligament,
depicted in pink, originates
on the fibula. The lateral
limb extends superiorly
and inserts onto the joint
capsule/lateral femoral
condyle. The medial
limb passes obliquely in
a superior and medial
direction and inserts on the
oblique popliteal ligament
of Winslow and the joint
capsule.
Injuries
• Yu et al. advocate using a coronal oblique sequence in the plane
of the intra-articular popliteus tendon to facilitate detection of the
finer PLC structures (see Fig. 13).
• Grading of injuries:
I: feathery edema around/within muscle, tendon, or ligament.
This is a strain or sprain (see Fig 14).
II: partial tear—edema with some continuous fibers. The
ligament/tendon may be abnormally thin or thick
(see Fig. 15).
III: complete tear: these are the ones that need to be fixed
(see Fig. 15, 20, 21).
• PFL best seen on coronal images attaching to medial fibular styloid
(see Fig. 16).
• Extensive edema around the PLC is worrisome for injury to one or
more of the PLC components. Even if no discrete tear is seen, PLC
injury should be suggested (see Fig. 17).
• Arcuate ligament: can’t be seen reliably: it’s quite thin and hugs the
capsule.
• Edema behind the capsule in the region of the popliteal hiatus:
suggestive of arcuate ligament injury (see Fig. 18)
• PCL, ACL, medial collateral ligament (MCL), and meniscal injuries
are commonly associated with injuries of the posterolateral corner
and should be sought (see Fig 19).
Figure 15: Biceps and FCL Injuries
12a
12b
21a
19b
21b
Corresponding Author:
Kirkland Davis, MD
University of Wisconsin—Madison
E3/311 CSC
600 Highland Avenue
Madison, WI 53792–3252
Ph: 608.265.4482 Fax: 608.263.0876
Email: [email protected]