Skeletal Radiol (2007) 36:729–735
DOI 10.1007/s00256-007-0298-2
SCIENTIFIC ARTICLE
Meniscofemoral ligaments: patterns of tears and pseudotears
of the menisci using cadaveric and clinical material
Marcelo R. de Abreu & Christine B. Chung &
Debbra Trudell & Donald Resnick
Received: 21 July 2006 / Revised: 2 January 2007 / Accepted: 19 February 2007 / Published online: 5 May 2007
# ISS 2007
Abstract
Purpose The purpose of the study was to determine the
different types of pseudotears of the posterior horn of the
lateral meniscus caused by the nearby meniscofemoral
ligaments (MFLs), and to correlate the presence of these
ligaments with patterns of meniscal tear.
Design Retrospective clinical study with patients and
prospective observatory study with cadaveric material.
Patients Magnetic resonance imaging studies of the knee in
49 patients who had subsequent arthroscopy of the knee
performed over a 1-year period at a single institution were
reviewed by two readers in consensus for the presence and
morphology of the MFLs of Humphry (LH) and Wrisberg
(LW). Ten cadaveric knee specimens were used for MRI,
anatomic, and histologic study.
Results The LH was present in 55% of patients, the LW in
94%, and both were present in 44.9%. The thickness of the
LH and LW ranged from 1–3 mm (mean 1.9, SD 0.61), and
from 1–3.8 mm (mean 1.8, SD 0.65) respectively (p>
0.05). A pseudotear in the posterior horn of the lateral
M. R. de Abreu : C. B. Chung : D. Trudell : D. Resnick
VA Health Care System, University of California San Diego,
La Jolla Village Drive, San Diego, CA 3655, USA
M. R. de Abreu
Hospital Mae de Deus,
Porto Alegre, Brazil
M. R. de Abreu
PPG Clinica Medica, Universidade Federal Rio Grande do Sul,
Rio Grande do Sul, Brazil
M. R. de Abreu (*)
Rua Costa 128,
CEP 90110-270 Porto Alegre, RS, Brazil
e-mail: [email protected]
meniscus was present in 63% of patients. In 13% the
pseudotear was vertically oriented, and in 87% the
pseudotear had an anterosuperior to posteroinferior orientation, ranging from 37 to 87°. There was no association
between the presence of one or both MFLs and the
occurrence of medial or lateral meniscal tears (p>0.05).
Conclusion Meniscofemoral ligaments are frequent anatomical structures that are found in the majority of knees
with MRI. They commonly cause a pseudotear of the
posterior horn of the lateral meniscus that can be simple,
double, or complex in appearance, with vertical or
anterosuperior to posteroinferior orientation.
Keywords Meniscofemoral ligaments .
Magnetic resonance imaging . Knee . Joint
Introduction
The meniscofemoral ligaments (MFLs) are structures that
attach the posterior horn of the lateral meniscus to the
femur. The most common of these, the posterior meniscofemoral ligament (of Wrisberg), serves to attach the
posterior horn of the lateral meniscus to the intercondylar
area of the femur, passing behind the posterior cruciate
ligament (PCL; Fig. 1).
Less common, the anterior MFL (of Humphry) serves to
attach the posterior horn of the lateral meniscus to the
intercondylar area of the femur, passing in front of the PCL
[1]. Whereas the attachment sites and course of the
ligaments are relatively uniform, their incidence is not.
Persons may have both, one, or none of the MFLs in each
knee [1, 2].
The accessory ligaments of Humphry and Wrisberg are
believed to increase the congruity between the meniscoti-
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Skeletal Radiol (2007) 36:729–735
horn of the lateral meniscus and other soft tissue structures
can be effectively investigated. By virtue of their anatomy,
the MFLs have been implicated in the false diagnosis of a
tear of the posterior horn of the lateral meniscus during
MRI [7]. The purpose of this study was to determine the
different types of pseudotears of the posterior horn of the
lateral meniscus caused by the insertion of nearby MFLs,
and to correlate the presence of these ligaments with
patterns of meniscal tear using MRI in a series of patients
and cadaveric specimens.
Materials and methods
Both the clinical and cadaveric part of the study were
approved by the Institutional Review Board. Informed
consent was obtained from patients or relatives as required.
Clinical study
Patients
Fig. 1 a Computer drawing (posterior view of the right knee)
demonstrating the meniscofemoral ligaments (MFLs) of Humphry
and Wrisberg, and the pseudotear zone (P). b Corresponding coronal
T1-weighted spin-echo MR image (600/14). PCL posterior cruciate
ligament, MM medial meniscus, LM lateral meniscus
bial socket and the lateral femoral condyle. This occurs
primarily during weight-bearing with the knee flexed and
the foot firmly fixed. The resultant anterior femoral
translation serves to tighten the meniscofemoral ligament
and draw the posterior horn of the lateral meniscus
anteromedially [3].
The MFLs are often the sole attachment of the posterior
horn of the lateral meniscus when there is no posterior
meniscal root [4]. The lateral meniscus, unlike the medial
meniscus, has no firm tibial or femoral peripheral attachments, which is one of the reasons for its increased mobility
compared with its counterpart [5]. Although it has been
generally thought that the MFLs always insert into the
femoral condyle, the MFL can insert into the PCL [6].
With magnetic resonance imaging (MRI), the identification of the MFLs and their relationship with the posterior
Forty-nine MRI studies of the knee in 49 patients (42 men,
7 women; age range 23–67 years; mean age 47.2 years, SD
12.8) who had subsequent arthroscopy of the knee
performed over a 1-year period at a single institution were
reviewed for the presence and morphology of MFLs. One
or both of these ligaments were considered present based
on the following imaging criteria: a ligamentous formation
greater than 0.5 mm in thickness originating from the
posterior horn of the lateral meniscus with a course adjacent
to the posterior cruciate ligament (PCL) and insertion into
the medial portion of the medial femoral condyle. If the
course of the ligament was anterior to the PCL it was
designated a ligament of Humphry and, if posterior, a
ligament of Wrisberg.
Imaging
Images were acquired with a 1.5-T MR imager (Signa; GE
Medical Systems, Milwaukee, WI, USA). In all cases,
imaging was performed in three standard planes with a
phased array knee coil with a 16-cm square field of view,
3-mm slice thickness with a 1-mm gap, matrix of 256×256,
and number of excitations between 2 and 3. The following
sequences were acquired: coronal spin echo (SE) T1weighted (360–850 ms/12–25 ms), coronal fat-suppressed
fast SE T2-weighted (3,200–4,400 ms/67–85 ms, echo train
length of 4 to 6), axial fat-suppressed fast spin echo (FSE)
Proton Density weighted (2,000–2,200 ms/20–40 ms),
sagittal fast spin echo (FSE) Proton Density weighted
(2,000–2,200 ms/20–40 ms), and sagittal short inversion
Skeletal Radiol (2007) 36:729–735
time inversion recovery (STIR; 3,000– 4,585 ms/34–60 ms/
150 ms [inversion time msec]) images. In 6 cases, SE T1weighted MR images with and without fat suppression were
acquired before and after intravenous administration of
0.1 mmo/kg gadopentetate-containing contrast material
(Magnevist; Berlex, Wayne, NJ, USA).
Image interpretation
The two musculoskeletal radiologists who retrospectively
analyzed the MRI studies of the knee in consensus were
asked to evaluate several parameters. Readers determined
the presence or absence of each MFL, its thickness, and the
presence or absence of a pseudotear in the posterior horn of
the lateral meniscus. The criterion used to establish the
presence of a pseudotear was the visualization of a linear
intermediate or high signal intensity zone in T1, T2 or proton
density-weighted images in at least 1 sagittal slice in the
posterior horn of the lateral meniscus extending to the
articular surface of the meniscus that, when followed in
subsequent slices, was seen to originate from the MFL. The
pseudotear generated by one or two MFLs was analyzed in
more detail regarding its extent, its angulations in the sagittal
plane with regard to the tibial plateau (see Fig. 2), and the
presence or absence of high signal intensity inside the
pseudotear in fluid sensitive images (T2-weighted, STIR).
Arthroscopy reports were recorded with regard to the
presence and location of meniscal tears.
Fig. 2 a Sagittal T1-weighted
spin echo MR image (600 ms/
20 ms) of a cadaveric knee
specimen obtained after the injection of a gadopentetate-containing contrast material
demonstrating the pseudotear
(white arrowhead) generated by
the connection of the ligament
of Wrisberg and the posterior
horn of the lateral meniscus and
the measurement of its angulation with regard to the tibial
plateau. b Corresponding Faxitron of the same cadaveric slice
showing fat density at the pseudotear. Meniscus (black arrow),
ligament of Wrisberg (white
arrow), and pseudotear (curved
arrow)
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Cadaveric study
Specimens
Eleven cadaveric knee specimens, harvested from unembalmed cadavers, were examined with radiography to
ensure integrity of the specimen and to exclude pathologic
bone or soft-tissue conditions. Ten fresh human knees
(8 men, 2 women; age range at death 70–88 years; mean
age at death 78 years) were subsequently selected for the
MRI and anatomic study. The cadaveric specimens were
immediately deep-frozen at −60°C (Bio-Freezer; Forma
Scientific, Marietta, OH, USA). None of the specimens had
evidence of surgical intervention or previous injuries in or
about the knee. The cadaveric specimens were allowed to
thaw for 18 h at room temperature prior to MRI.
Subsequently, the cadaveric specimens were prepared
according to methods described in the literature [8].
Imaging
Magnetic resonance images were acquired with a 1.5-T
superconducting MR imager (Signa; GE Medical Systems,
Milwaukee, WI, USA) with two 5-inch standard flexible
surface coils (Flex Coil; Medical Advances, Milwaukee,
WI, USA) positioned posteromedially and posterolaterally
at the menisci level. All cadaveric knees were placed in a
neutral position and immobilized with foam pads. Imaging
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Skeletal Radiol (2007) 36:729–735
was performed in the coronal, transverse, and sagittal
planes. The MRI protocol consisted of T1-weighted spinecho (SE) sequences (repetition time ms/echo time ms=
600/20–23). To acquire a higher signal-to-noise ratio, a
section thickness of 2.5 mm with a space gap of 0.5 mm
was used. The field of view was 12×12 cm in the sagittal,
coronal, and axial planes, and the data acquisition matrix was
512×256 pixels. SE T1-weighted MR images in sagittal,
coronal, and axial planes with and without fat suppression
were acquired before and after intrarticular administration of
15 ml of a gadopentetate-containing contrast agent solution
at 1% concentration (Magnevist). MRI studies were evaluated by the consensus of two musculoskeletal radiologists
with emphasis on the MFLs of the knee.
Knee sectioning
After MRI was performed, the cadaveric specimens were
frozen again at −60°C for more than 96 h and were
subsequently sectioned in the sagittal plane with a band saw
into 3-mm-thick slices. Each sagittal slice (23 slices per
patient; 10 patients) was photographed and imaged with
high resolution radiography (Faxitron; Hewlett Packard,
McMinnville, OR, USA). To determine the anatomic
relationships of the MFLs with the meniscus and surrounding structures, the findings at MRI were correlated with
those derived from inspection of cadaveric sections. The
cadaveric study was analyzed by the consensus of two
musculoskeletal radiologists, the same ones who performed
evaluation of the clinical study.
Table 2 Number of sagittal slices in which the pseudotear was
observed with MRI in 49 patients
Number of sagittal slices
1
2
3
4
Total pseudotears
Ligament present (%)
6 (19)
15 (48)
8 (26)
4 (6)
31 (100)
were stained using the hematoxylin-eosin technique. Histologic sections were analyzed at light microscopy (magnification, 34 to 3,100) in consensus by a musculoskeletal
radiologist and an experienced orthopedic pathologist
(30 years’ experience in orthopedic pathology). The
examiners recorded in consensus the presence of the
pseudotears and its tissue composition.
Results
Clinical study
The frequency of MFLs in the study patients is shown in
Table 1. A pseudotear in the posterior horn of the lateral
Histology
To analyze the tissue composition of the pseudotears
generated by the MFLs and its intimate relationship with
adjacent structures at its insertion site, histologic samples of
this area were collected in 3 knee specimens. Samples were
suspended in a 10% formalin solution for histologic
analysis immediately after inspection of the cadaveric
specimens. Specimens were embedded in paraffin and
sectioned further into 5-μm-thick slices. Histologic sections
Table 1 Frequency of meniscofemoral ligaments (MFLs) in 49
clinical patients
Presence (%)
Humphry
Wrisberg
Both ligaments
Total patients
27 (55)
46 (94)
22 (45)
49
Mean thickness,
mm (range)
1.9 (1–3)
1.8 (1–3.8)
Average angle
of pseudotear
63
58
No statistic difference between thickness or average angle (p>0.05).
All patients had at least one MFL
Fig. 3 Sagittal proton density (PD)-weighted fast spin-echo MR
image (2,200 ms/40 ms) in a 36-year-old woman demonstrating the
anatomic configuration of the posterior compartment of the knee
between the PCL and the lateral meniscal root (mr), with the MFLs of
Humphry (white arrow), Wrisberg (white arrowhead), and joint
capsule (black arrowhead)
Skeletal Radiol (2007) 36:729–735
meniscus was present in 63% of patients (31 out of 49). The
numbers of sagittal slices in which the pseudotear was
observed varied from 1 to 4 and are summarized in Table 2.
Fluid in the pseudotear was observed in 10% of cases (5 out
of 31). In 13% (4 out of 31) the pseudotear was vertically
oriented, and in 87% (27 out of 31) the pseudotear had an
orientation from anterosuperior to posteroinferior, ranging
from 37 to 87° (mean 60.6°, SD 17.6). The angle of the
pseudotears generated by ligament of Wrisberg (63°) and
ligament of Humphry (58°) did not differ statistically (p<0.05).
When both ligaments were present (45%, 22 out of 49) 1
pseudotear was visualized in 14 patients, 2 pseudotears in 2
patients (see Fig. 3), and no pseudotear in 6 patients. Two
pseudotears were observed in 2 additional patients caused
by 1 MFL and the joint capsule. When both ligaments were
present and there was 1 pseudotear, the pseudotear
corresponded to the ligament of Wrisberg in 39%, and to
the ligament of Humphry in 15%; in 46% of cases, the
ligament causing the pseudotear could not be determined.
On arthroscopic examination, medial meniscus tears
were seen in 65% (32 out of 49) of patients in one or two
locations: in the anterior horn in 3% (1 out of 33), in the
body in 9% (3 out of 33), in the posterior horn in 72% (24
out of 33), and as a bucket handle tear in 15% (5 out of 33).
The lateral meniscus was torn in 25% (12 out of 49): a tear
in the body was seen in 42% (5 out of 12) and in the
posterior horn in 58% (7 out of 12). In 1 case a tear of the
posterior horn of the lateral meniscus was noted to happen
at the insertion site of the MFL of Wrisberg (see Fig. 4).
There was no association between the presence of one or
both MFLs and the occurrence of medial or lateral meniscal
tears (p>0.05).
Fig. 4 a Sagittal PD-weighted
fast spin-echo MR image
(2,200 ms/40 ms) in a 30-yearold man with an arthroscopically
proven tear at the MFL insertion
site, demonstrating a wide space
between the ligament of
Wrisberg (white arrowhead) and
the posterior horn of the lateral
meniscus (white arrow).
b Lateral slice of the same knee
demonstrating a vertical tear
(arrowhead) at the pseudotear
location
733
Cadaveric study
The ligament of Humphry was present in 5 knees and the
ligament of Wrisberg in 7 knees. Both MFLs were present
in 5 knees. There was no knee joint without at least 1
meniscofemoral ligament. A pseudotear of the posterior
horn of the lateral meniscus was present in 6 joints (see
Fig. 5); in 1 knee there were 2 pseudotears, 1 caused by the
ligament of Wrisberg and the other by the ligament of
Humphry (see Fig. 6). The angle of the pseudotears ranged
from 45–75°. In 3 knee specimens the pseudotear was seen
in only 1 section, in 2 specimens in 2 sections, and in 1
specimen in 3 sections. In specimen number 2, there was no
evidence of a meniscal root and the meniscofemoral
ligaments were the only insertion structure of the posterior
horn of the lateral meniscus; in specimen number 3, the
ligament of Wrisberg inserted into the joint capsule and not
into the lateral meniscus; and in specimen number 6 the
ligament of Wrisberg was bifid.
Results of histology
On histological study of the site of the pseudotear in the
posterior horn of the lateral meniscus, the MFLs showed
architecture and composition very similar to the adjacent
meniscal tissue. Collagen fibers were responsible for the
majority of MFLs, with their orientation very similar to the
fibers of the external margin of the adjacent meniscus. All
histologic samples collected in 3 knee specimens showed a
pseudotear caused by the MFLs. The space between the
MFL and the meniscus (the pseudotear) was composed of a
gap in the density of the collagen fibers of the MFL and of
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Skeletal Radiol (2007) 36:729–735
Discussion
Fig. 5 Sagittal cadaveric slice acquired at the level of the posterior
horn of the lateral meniscus showing the pseudotear (arrowheads)
caused by the MFL of Wrisberg after its connection with the
meniscus. M meniscus, W ligament of Wrisberg
orientation of these fibers in a different direction. A small
quantity of fat intermixed with the collagen fibers was also
noted at the site of the pseudotear.
Fig. 6 a Sagittal T1-weighted
spin echo MR image (600 ms/
20 ms) of a cadaveric knee
specimen obtained after the injection of a gadopentetate-containing contrast material
demonstrating the connection of
the MFLs of Humphry (H) and
Wrisberg (W) with the posterior
horn of the lateral meniscus
generating two pseudotears.
b Corresponding sagittal cadaveric slice acquired at the same
level. c Corresponding Faxitron
showing the collagen fibers
structure of the ligament of
Humphry (black arrow) and
Wrisberg (white arrow).
d Corresponding histology
(hematoxylin-eosin stain; objective magnification×10) at the
same level
The high incidence of MFLs shown in our clinical study
(Humphry ligament, 55%; Wrisberg ligament, 94%) is in
agreement with the results of two recent anatomical studies
[9, 10]. Other studies have reported an incidence of MFLs
that varied from 71 to 80% of knees [1, 3]. Although some
reports suggest that the ligament of Humphry is thinner
than the ligament of Wrisberg [3], others suggest that when
one ligament is thin or absent, the other is thick [10]. Our
results showed no difference between the sizes of the MFLs
on cross-sectional measurement.
The pseudotear caused by the high signal band located
between the MFLs and the posterior horn of the lateral
meniscus was seen frequently (63%) on the MR images of
our patients. The lack of visualization of a pseudotear in 37%
of patients with MFLs was probably related to the slice
thickness used in MR imaging and also to the presence of thin
structures traveling in oblique planes. When present, the
pseudotear was visualized in 1 (19%), 2 (48%), 3 (26%), or 4
(6%) sagittal slices. When seen in only 1 sagittal slice, the
pseudotear could be caused by a volume average artefact of
the MFL connection with the meniscus. The visualization of
the pseudotear in multiple continuous sagittal slices was
Skeletal Radiol (2007) 36:729–735
dependent on the type of insertion of the MFL. In cases in
which it inserted with a vertical orientation, it was seen on just
1 image; in cases in which it paralleled the posterior horn of
the lateral meniscus, it was seen on more than 1 sagittal image.
As an estimate, with a slice thickness of 3 mm and an
interslice gap of 1 mm, visualization of the pseudotear on 4
sagittal images implies that the MFL extended parallel to the
posterior horn of the lateral meniscus for about 16 mm. Steep
angles of the MFLs create more pseudotears. The orientation
of the pseudotears was always from an anterosuperior to a
posteroinferior direction with angulation varying from 37 to
90°, and a few cases with a vertical angle (90°). The degree of
angulation of the pseudotears did not differ according to
which MFL was present. The visualization of just one
pseudotear when both ligaments were present (14 out of 22)
suggests that the MFLs connect with each other before they
connect to the lateral meniscus
Although some authors consider that the ligaments of both
Humphry and Wrisberg are anterior and posterior branches of
one meniscofemoral ligament [11], we prefer, as do other
authors [3, 12], to consider the MFLs as individual
ligaments. In support of this, we observed in 2 patients 2
pseudotears in the same sagittal slice, each corresponding to
1 individual MFL. This appearance has not yet been
described in the literature. In 2 patients and in 1 cadaveric
specimen, however, the presence of two pseudotears in one
sagittal slice was related to a single MFL and the insertion of
the capsule into the meniscus. In 4 patients, high signal on
fluid-sensitive sequences was observed in the pseudotear.
The fluid between the MFL and the posterior horn of the
lateral meniscus could be related to a groove in the proximal
insertion of the MFL as the fluid was observed on only one
sagittal image. Furthermore, the cadaveric and histological
study revealed that there were collagen fibers and small
amounts of fat between the MFL and the meniscus.
In 1 cadaveric specimen there was an absence of the
posterior root ligament attachment of the lateral meniscus. In
this case the only insertion into the posterior horn of the lateral
meniscus was the MFL. This variant has been described by
other authors [4]. We believe that the absence of this
posterior root ligament is more frequent than reported.
Although there have been few reports regarding the
function of the MFLs, these accessory structures are
believed to increase the congruity between the meniscus
and articular surface in the posterolateral aspect of the knee
joint. According to Friederich and O’Brien [12], the
ligament of Humphry becomes tenser during knee flexion,
stabilizing the posterior horn of the lateral meniscus during
that motion. The ligament of Wrisberg is believed to
provide meniscal stability during knee extension [12]. Also,
during external rotation of the femur on the tibia, the
posterior horn of the lateral meniscus is drawn anteromedially by the ligament of Humphry. It is believed that the
735
combined action of the popliteus muscle through its
aponeurotic meniscal attachment is important, improving
“controlled” meniscal motion.
As a safeguard against lateral meniscal injuries during
knee motion, the MFLs probably have a similar function;
the absence of one is compensated for by the hypertrophy
of the other, as indicated by other authors [10]. The lack of
correlation between the frequency of arthroscopically
evident meniscal tears and the presence of one or other
MFL reinforce this idea.
We recognize that our study has several limitations. First,
the number of patients was relatively small.. The study was
also retrospective in nature and we did not have sufficient
patient clinical information. Our MRI observations were
confined to the sagittal plane. The anatomical study was
done in a small number of cadaveric knees derived from
elderly persons with some degree of osteoarthritis. The
histological analysis was made only in a few selected cases.
Meniscofemoral ligaments are frequent anatomical structures that are found in the majority of knees on MRI. They
commonly cause a pseudotear of the posterior horn of the
lateral meniscus that can be simple, double, or complex in
appearance, with a vertical or anterosuperior to posteroinferior orientation.
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