AJR 2003; 180:647-653
© American Roentgen Ray Society
MR Imaging of the Anatomy of and Injuries to the Lateral and Posterolateral Aspects of the Knee
Andrew H. Haims1,
Michael J. Medvecky2,
Raymond Pavlovich, Jr.2 and
Lee D. Katz1
1 Department of Radiology, Yale University School of Medicine, 333 Cedar St., P.
O. Box 208042, New Haven, CT 06520-8042.
2 Department of Orthopedic Surgery, Yale University School of Medicine, New
Haven, CT 06520-8042.
Received April 2, 2002;
accepted after revision August 13, 2002.
Address correspondence to A. H. Haims.
The lateral and posterolateral aspects of the knee have gained attention in
recent years both for their complex anatomy and their clinical relevance.
Injuries to the posterolateral corner and lateral structures of the knee are
infrequent and are usually associated with anterior or posterior cruciate
ligament tears or a combination of both
[1]. The significance of a
missed injury can be profound; reconstructed anterior or posterior cruciate
ligaments can fail, and unrecognized injuries may also lead to pain,
instability, and possibly degenerative changes
[2]. Physical examination in
the acutely injured, nonanesthetized or polytrauma setting may be difficult
because of pain, guarding, swelling, or associated injuries. Symptoms related
to the posterolateral corner may also be masked in these situations. MR
imaging is invaluable in evaluating normal anatomy and diagnosing injuries to
the lateral structures of the knee and in providing essential preoperative
information [3,
4,
5]. Although indirect evidence
of injury to some of the lateral structures may be obtained arthroscopically,
most often open exploration is needed to analyze and repair these structures.
In this pictorial essay, we use MR imaging to illustrate both the normal
structures of the lateral and posterolateral aspects of the knee and the
various injury patterns, and we briefly comment on treatment.
The anatomy of the lateral and posterolateral aspects of the knee can be
difficult to understand because of the number of structures and their
variability both in form and nomenclature. The structures of the lateral and
posterolateral aspects of the knee reviewed in this article consist of the
iliotibial band, popliteus muscle and tendon, popliteofibular ligament, biceps
femoris tendon, lateral collateral ligament (fibular collateral ligament),
lateral gastrocnemius tendon, fabellofibular ligament, and mid third lateral
capsular ligament (Fig. 1A,
1B). We do not comment on the
additional structures of the lateral and posterolateral aspects of the knee
because of the lack of consistent visualization both at imaging and
dissection.
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Fig. 1A. —Anatomic drawings illustrate structures of lateral and
posterolateral knee. (Courtesy of Beltran S, Albons, Gerona, Spain) Lateral
drawing shows insertion of iliotibial band, 1; mid third capsular ligament, 2;
lateral collateral ligament, 3; fabellofibular ligament, 4; and popliteus
muscle and tendon, 5.
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Fig. 1B. —Anatomic drawings illustrate structures of lateral and
posterolateral knee. (Courtesy of Beltran S, Albons, Gerona, Spain) Posterior
drawing shows biceps femoris tendon attachment, 1; lateral collateral
ligament, 2; popliteofibular ligament, 3; and popliteus muscle and tendon,
4.
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The iliotibial band is a combination of the tendon of the tensor fascia
lata and the deep and superficial fibers of the fascia lata. The iliotibial
band consists of deep and superficial layers. The superficial layer is the
main tendinous component and inserts onto Gerdy's tubercle on the anterior
lateral tibia [6]
(Fig. 2). The deep layer
inserts on the intermuscular septum of the distal femur
[4]. Isolated tears of the
iliotibial band are rare, but these tears may occur in patients with injuries
to multiple ligaments of the knee, including complete transection or avulsion
of its tibial insertion (Fig.
3A,
3B,
3C). If part of a broader
injury pattern, repair of a ruptured iliotibial band is generally
indicated.
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Fig. 2. —Normal appearance of iliotibial band. Coronal fast spin-echo
proton density-weighted MR image of 24-year-old woman shows insertion of
superficial fibers of iliotibial band (arrows) on Gerdy's tubercle of
anterior tibia. This tendinous insertion is main one for iliotibial band.
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Fig. 3A. —Injuries to iliotibial band. Coronal fast spin-echo proton
density-weighted MR image illustrates disruption of fibers of iliotibial band
(arrows) in 34-year-old man with multiple ligamentous knee
injuries.
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Fig. 3B. —Injuries to iliotibial band. Coronal fast spin-echo proton
density-weighted MR image shows avulsion and retraction of iliotibial band
(arrows) and its tibial donor site (arrowheads) in
18-year-old woman injured in motor vehicle crash.
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The popliteus tendon originates on the anterior aspect of the popliteus
groove just anterior and inferior to the origin of the lateral collateral
ligament and extends inferiorly and medially to insert on the posterior medial
aspect of the tibia (Fig. 4A,
4B). The popliteus tendon has
strong attachments to the lateral meniscus posteriorly. The popliteofibular
ligament, one of the most important stabilizers in the posterolateral corner
[7], inserts on the posterior
medial fibular styloid and attaches to the popliteus tendon just proximal to
the myotendinous junction (Fig.
5). Injuries to the popliteus musculotendinous junction or femoral
insertion are common in high-grade injuries to the posterolateral corner of
the knee (Fig. 6A,
6B,
6C,
6D). Acute repair or
reconstruction is performed when operative treatment of combined injuries is
undertaken. Isolated injuries are less common.
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Fig. 4A. —Normal appearance of popliteus tendon. Coronal fast spin-echo
proton density-weighted MR image shows femoral attachment of popliteus tendon
in anterior aspect of popliteus groove (arrows) in 14-year-old
boy.
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Fig. 5. —Normal appearance of popliteofibular ligament. Coronal fast
spin-echo proton density-weighted MR image of 28-year-old woman illustrates
origin of popliteofibular ligament on medial fibular styloid (black
arrow) and insertion on popliteus tendon just proximal to myotendinous
junction (white arrow).
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Fig. 6A. —Injuries to popliteus tendon. Coronal fast spin-echo proton
density-weighted MR image shows abnormal signal at femoral origin of popliteus
tendon (arrows) in 34-year-old man with surgically confirmed
tear.
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Fig. 6D. —Injuries to popliteus tendon. Sagittal fast spin-echo
fat-suppressed T2-weighted MR image of 22-year-old woman shows edema at
myotendinous junction of popliteus (arrows), consistent with partial
tear in this region.
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The biceps femoris tendon consists of long and short heads. In this
article, we discuss only the insertions of the direct arms of both the long
and short heads. The long head inserts onto the middle of the posterolateral
aspect of the fibula, and the short head inserts just medial to the long head.
These insertions cannot be seen as separate
(Fig. 7). Injuries to the
biceps femoris tendon are seen in conjunction with posterolateral ligamentous
injuries in the knee. Biceps femoris imjuries are most commonly described as
avulsion or partial avulsion injuries or as tears of the distal myotendinous
junction (Fig. 8A,
8B). An association of partial
tendinous avulsion in conjunction with Segond fractures has been described as
well. In patients with acute injuries, primary repair is usually undertaken
with repair of all injured structures.
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Fig. 7. —Normal appearance of biceps femoris tendon. Coronal fast
spin-echo proton density-weighted MR image of 29-year-old woman shows long and
short heads of biceps femoris tendons (arrows) inserting into lateral
aspect of fibular styloid.
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Fig. 8B. —Injuries of biceps femoris tendon. Coronal fast spin-echo
T2-weighted MR image illustrates edema at myotendinous junction of biceps
femoris (arrows) consistent with tear in 21-year-old female
gymnast.
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The lateral collateral ligament (fibular collateral ligament) arises from
the lateral femoral condyle and inserts on the lateral aspect of the middle
third of the fibular head, sometimes joining the biceps femoris tendon
(Fig. 9). This ligament has a
posterior and oblique course and is seldom seen entirely on one coronal image.
The lateral collateral ligament can be injured in isolation or in conjunction
with other knee ligamentous structures, especially those of the posterolateral
corner and the cruciate ligaments. The location of the injury relative to the
lateral collateral ligament can be proximal, mid substance, or at the tibial
insertion (Fig. 10A,
10B,
10C). First- or second-degree
lateral collateral ligament sprains are usually treated nonoperatively with
protected mobilization and rehabilitation. Third-degree lateral collateral
ligament sprains or combined ligament injuries are usually treated with early
operative repair, augmentation, or reconstruction.
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Fig. 9. —Normal appearance of lateral (fibular) collateral ligament.
Coronal fast spin-echo proton density-weighted MR image of 29-year-old woman
shows course of lateral collateral ligament (arrows), extending from
lateral femoral condyle to lateral aspect of fibular head. This ligament
frequently has oblique course and often must be visualized on sequential
coronal MR images.
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Fig. 10A. —Various injury patterns of lateral (fibular) collateral
ligament depicted on coronal fast spin-echo proton density-weighted MR
imaging. Image shows tear of proximal fibers of lateral collateral ligament
(arrows) in 21-year-old woman.
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Fig. 10B. —Various injury patterns of lateral (fibular) collateral
ligament depicted on coronal fast spin-echo proton density-weighted MR
imaging. Image illustrates complete disruption of midsubstance of lateral
collateral ligament (arrows) in 34-year-old man.
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Fig. 10C. —Various injury patterns of lateral (fibular) collateral
ligament depicted on coronal fast spin-echo proton density-weighted MR
imaging. Image shows avulsion and retraction of lateral collateral ligament
(arrows) in 18-year-old man.
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The lateral gastrocnemius tendon inserts on the supracondylar process of
the femur just posterior to the lateral collateral ligament
(Fig. 11). Injuries to this
tendon are uncommon [4]. The
fabellofibular ligament attaches to the posterolateral aspect of the fabella
and inserts on the fibular styloid (Fig.
12A,
12B). This ligament can be
present even in the absence of a fabella
[6].
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Fig. 11. —Normal appearance of femoral origin of lateral head of
gastrocnemius tendon. Sagittal T1-weighted MR image of 27-year-old woman shows
origin of lateral head of gastrocnemius tendon in supracondylar process of
lateral femur (arrows).
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Fig. 12A. —Normal variations of fabellofibular ligament. Coronal fast
spin-echo proton density-weighted MR image of 19-year-old woman illustrates
attenuated appearance of normal fabellofibular ligament (arrows),
extending from posterolateral aspect of fabella to fibular styloid.
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Fig. 12B. —Normal variations of fabellofibular ligament. Coronal fast
spin-echo proton density-weighted MR image of 23-year-old man shows similar
but more robust appearance of normal fabellofibular ligament
(arrows).
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The mid third lateral capsular ligament is a thickening of the lateral
joint capsule with attachments to the femoral condyle and lateral tibia. The
tibial attachment is just below the articular surface and just posterior to
Gerdy's tubercle (Fig. 13).
Capsular attachments to the lateral meniscus are also present. Bony avulsion
at the tibial attachment of the mid third lateral capsular ligament is also
known as a Segond fracture [8]
(Fig. 14A,
14B). This fracture has a high
association (92%) with anterior cruciate ligament injury.
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Fig. 13. —Normal appearance of mid third lateral capsular ligament.
Coronal fast spin-echo proton density-weighted MR image of 36-year-old woman
shows tibial attachment of mid third lateral capsular ligament
(arrows), which is just below articular surface and just posterior to
attachment of superficial fibers of iliotibial band.
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Fig. 14A. —16-year-old boy with avulsion of mid third lateral capsular
ligament (Segond fracture) and associated anterior cruciate ligament tear.
Coronal fast spin-echo proton density-weighted MR image shows bony avulsion of
mid third capsular ligament (arrowheads) and medial collateral
ligament tear (black arrows). Anterior cruciate ligament tear
(white arrows) can also be seen.
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Fig. 14B. —16-year-old boy with avulsion of mid third lateral capsular
ligament (Segond fracture) and associated anterior cruciate ligament tear.
Sagittal fast spin-echo fat-suppressed T2-weighted MR image shows disruption
of fibers of anterior cruciate ligament (arrows).
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Ross et al. [3] showed that
an anterior medial femoral condylar bone bruise, sometimes associated with an
anterior tibial bone bruise, was a consistent finding in all five of their
patients with acute posterolateral corner injuries
(Fig. 15). These authors note
that the medial femoral contusion is evidence of a hyperextension varus
movement associated with many posterolateral corner injuries.
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Fig. 15. —Bone bruising pattern frequently associated with acute
injuries to posterolateral corner. Sagittal fat-suppressed fast spin-echo
T2-weighted MR image illustrates bone bruises (arrows) in anterior
medial femur in 21-year-old woman with acute posterolateral corner injury (as
shown in Figs. 8B and
10A).
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The "arcuate" sign or fracture is an avulsion fracture of the
fibular head and styloid at the attachment of the lateral collateral ligament
and biceps femoris tendon, and the MR imaging findings associated with this
avulsion fracture have recently been described
[9]. Although the avulsion
fracture may occasionally not be visualized on conventional radiographs, the
presence of edema in the proximal fibula can be a helpful sign of this injury
(Fig. 16A,
16B,
16C).
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Fig. 16A. —MR imaging equivalent of "arcuate" sign in
16-year-old boy with recent knee dislocation. Sagittal fast spin-echo
fat-suppressed T2-weighted MR image shows edema in proximal fibula
(arrows), consistent with avulsion injury at insertion of biceps
femoris tendon and lateral collateral ligament.
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Fig. 16B. —MR imaging equivalent of "arcuate" sign in
16-year-old boy with recent knee dislocation. Coronal oblique fast spin-echo
proton density-weighted MR image shows avulsion and retraction of biceps
femoris tendon (arrows).
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Fig. 16C. —MR imaging equivalent of "arcuate" sign in
16-year-old boy with recent knee dislocation. Coronal oblique fast spin-echo
proton density-weighted MR image illustrates avulsion, retraction, and lateral
displacement of lateral collateral ligament (large arrows). Partial
avulsion of femoral attachment of popliteus tendon (small arrows) is
also present.
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In conclusion, MR imaging can provide an excellent and noninvasive means of
evaluating the complex anatomy and injury patterns of the lateral and
posterolateral structures of the knee and assisting in the preoperative
planning of these injuries.
Acknowledgments
We thank Salvador Beltran for his work on the anatomic drawings.
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