The posterolateral corner (PCL) of the knee: Dynamic
evaluation with high-resolution ultrasound (D-HRUS)
Poster No.:
C-2205
Congress:
ECR 2010
Type:
Educational Exhibit
Topic:
Musculoskeletal
Authors:
F. Paparo , G. Grillo , L. Altafini , L. M. Sconfienza , E. Silvestri ;
1
1
1
1
2
1
2
Genova/IT, San Donato Milanese (MI)/IT
Keywords:
knee, posterolateral corner, ultrasound
DOI:
10.1594/ecr2010/C-2205
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Page 1 of 13
Learning objectives
The purpose of our educational exhibit is to describe the normal sonographic anatomy
of the PLC of the knee integrated with dynamic manoeuvers.
Background
The PLC of the knee is a group of structures that together form a functional complex
of muscles, tendons, capsule, and ligaments. The main function of this complex is to
oppose the internal rotational and translational forces that act on the knee. It is also
effective in stabilizing the joint against varus movements. The PLC of the knee can
be evaluated by magnetic resonance imaging (MRI). However, due its complexity
and its superficial location, PLC visualization can be suboptimal. In addition, MRI
evaluation of PLC can be limited by the exam performed with the knee in extension.
Finally, some PLC injuries are only highlighted under stress, a condition that can be
hardly reproduced during a MRI scan. HRUS seems to be the ideal imaging technique
to evaluate the PLC of the knee. In fact, its very superficial location is easily and
effectively reached using a high-resolution broadband linear array transducer (up to
18 MHz). Then, HRUS has the great advantage to examine the knee during flexoextension movements and under stress (e.g. with the patient standing on the floor),
thus revealing small tears otherwise undetectable. Moreover, HRUS is cheaper and
more readily available compared to MRI and can be used to perform an immediate
comparative evaluation of the counterlateral knee. A number of previous studies both
on cadavers and in living subjects described the sonographic appearance of normal
anatomy of the PLC of the knee. However, none of them presents any dynamic image
of such structures.
Imaging findings OR Procedure details
POPLITEUS MUSCLE AND TENDON Popliteus muscle and its tendon are the main
dynamic stabilizers of the PLC of the knee. It takes origin proximally from the middle
facet of the lateral surface of the lateral femoral condyle and inserts distally onto
the posterior tibia. The tendon is intracapsular and runs behind the posterior wall of
lateral meniscus where it gives some extensions. The function of the popliteus muscle
is to rotate the femur on the tibia and assists the flexion of the leg upon the thigh.
POPLITEOFIBULAR LIGAMENT Popliteofibular ligament is the main static stabilizer
of the PLC of the knee. Popliteofibular ligament has a significant role in preventing
excessive posterior translation and varus angulation, and in restricting excessive
primary and coupled external rotation. It is a ligamentous structure descending from
Page 2 of 13
the musculotendinous junction of the popliteus to the posterosuperior prominence
of the fibular head, just adjacent to the insertion of the LCL. Half of this ligament
is partially covered by the origin of the LCL. The arcuate ligament hides partially
the PFL and it blends with it. In its distal two-thirds the orientation of the fibres of
the popliteofibular ligament is nearly vertical and similar to that of the LCL. In its
proximal one-third it fuse with the popliteal tendon and is orientated more obliquely.
LATERAL COLLATERAL LIGAMENT The LCL is a round ligament that lies beneath
the tendon of the biceps femoris muscle and runs from the lateral epicondyle, anterior
to the origin of the gastrocnemius muscle, to the fibular head where it blends with
the biceps femoris tendon. The LCL lies just posterior to mid-axial point of the knee
and is the primary restraint to varus stress in the knee. The LCL is not connected
with the meniscal capsule but it is separated by a thin fat pad. The LCL is tight when
the knee is extended and it becomes loose when flexion exceeds 30°. BICEPS
FEMORIS TENDON The biceps femoris tendon is a strong stabilizer of the PLC
of the knee. The tendon inserts into the anterolateral side of the head of the fibula,
and by a small slip into the lateral condyle of the tibia. At its insertion the tendon
divides into two portions, which embrace the lateral collateral ligament of the kneejoint. From the posterior border of the tendon a thin expansion is given off to the
fascia of the leg. Both heads of the biceps femoris perform knee flexion and help the
extrarotation of the leg. LATERAL HEAD OF THE GASTROCNEMIUS Although the
main function of gastrocnemious is plantar flexion, the lateral head acts as an important
dynamic stabilizer of the PLC of the knee. The lateral head arises from the lower
posterior surface of the femur above the lateral condyle, embedding also the fabella,
when present. The tendon is very shorts and almost immediately it blends into the
myotendineous junction.
FABELLOFIBULAR LIGAMENT The fabellofibular ligament inserts on the apex of
fibular styloid process and ascends vertically to lateral head of gastrocnemius where
it blends with posterior termination of oblique popliteal ligament. The fabellofibular
ligament is found deep between biceps tendon and lateral head of gastrocnemius.
The fabellofibular ligament alone reinforces capsule in 20% when arcuate ligament is
missing. When fabella is large, fabellofibular ligament is large, but arcuate ligament is
not usually present.
ARCUATE LIGAMENT The arcuate ligament is an extracapsular ligament of the PLC
of the knee. It is usually Y-shaped, even though it can also be fan-shaped when fabella
is missing. The main insertion is on the fibular head. From there, one arm runs over
popliteus muscle and attaches on the posterior middle tibia. This arm could be missing
when fabella is absent. The other arm blends with the proximal insertion of the lateral
head of gastrocnemius on the lateral epicondyle of the femur.
LATERAL GENICULATE ARTERY This structure is not properly a part of the PLC of
the knee. However, knowing its anatomy is fundamental when evaluating such region,
as it serves as an important anatomical landmark. Arising from the popliteal artery, it
runs inferolaterally around the knee. In the PLC, it runs deeply to the lateral collateral
ligament and superficially to the popliteofibular ligament.
Images for this section:
Page 3 of 13
Fig. 1: Popliteus muscle and tendon. F=femur; T=tibia; LM=lateral meniscus; white
arrows=popliteus tendon; yellow arrows=popliteus muscle; asterisk=anisotropy artifact
that hinders the proximal enthesis of popliteus tendon.
Page 4 of 13
Fig. 2: Popliteofibular ligament. F=femur; T=tibia; LM=lateral meniscus; white
arrows=popliteus tendon; yellow arrows=popliteus muscle; asterisk=anisotropy artifact
that hinders the proximal enthesis of popliteus tendon.
Fig. 3: Lateral collateral ligament. Extended field of view scan (EFOV) of the PLC of the
knee. F=femur; T=tibia; LM=lateral meniscus; Fi=fibula; asterisk=popliteus tendon; white
arrows=lateral collateral ligament.
Fig. 4: Biceps femoris muscle and tendon. F=femur; T=tibia; LM=lateral meniscus;
Fi=fibula; white arrows=biceps femoris tendon; yellow arrows=biceps femoris
myotendineous junction.
Page 5 of 13
Fig. 5: Lateral head of the gastrocnemius. F=femur; white arrows=lateral head of
gastrocnemius muscle; asterisk=tendon insertion.
Fig.
6:
Fabellofibular
ligament.
arrows=fabellofibular ligament.
Fa=fabella;
F=femur;
Fi=fibula;
white
Page 6 of 13
Fig. 7: Arcuate ligament. F=femur; T=tibia; Fi=fibula; white arrows=arcuate ligament;
asterisk=lateral collateral ligament; yellow arrow=lateral geniculate artery.
Fig. 8: Lateral geniculate artery. F=femur; PF=popliteofibular ligament; white
arrows=lateral collateral ligament; asterisks=lateral geniculate artery.
Page 7 of 13
Fig. 9: Dynamic evaluation of popliteofibular ligament during slight flexion of the knee
and internal rotation.
Page 8 of 13
Fig. 10: Dynamic evaluation of lateral collateral ligament during flexion of the knee and
slight internal rotation.
Page 9 of 13
Fig. 11: Dynamic evaluation of biceps femoris during slight flexion of the knee and internal
rotation.
Page 10 of 13
Conclusion
HRUS is effective in the depiction of normal anatomy of the PLC of the knee.
The dynamic evaluation of PLC structures is effective to understand the complex
mechanism of stabilization of such area. Further studies on patients with PLC instability
are needed to establish the clinical role of dynamic HRUS in the evaluation of such
area.
Personal Information
1
2
1
1,3
Francesco Paparo , Giovanna Grillo , Luisa Altafini , Luca M Sconfienza
, and Enzo
4
Silvestri
1
Radiology Unit, Department of Internal Medicine
University of Genova School of Medicine, Genova, Italy
2
Radiology Unit, Ospedale Santa Corona, Pietra Ligure, Italy
3
Radiology Unit, IRCCS Policlinico San Donato, San Donato Milanese, Italy
4
Radiology Unit, Ospedale Evangelico Internazionale, Genova, Italy
Contact: io@lucasconfienza.it
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