Although meniscofemoral ligaments are distinct anatomic units, their anatomy and function are controversial from an anatomic and radiologic point of view. Five hundred knee MR examinations were retrospectively studied in an effort to demonstrate the incidence and variations regarding sex and age distribution, as well as the anatomy of the meniscofemoral ligament at magnetic resonance imaging. Patients were mostly men, three hundred and twelve, in contrast with women who were fewer, one hundred eighty-eight patients. The mean age of the patients who were included in this study was 46 years. More than half of them were between 20 and 40 years old; one hundred thirty-three patients among 20 to 30 years old and one hundred and one patients among 31 and 40 years old, in total two hundred thirty-four patients.
An imaging breakthrough had led us to pay more attention in small anatomic structures such as the meniscofemoral ligaments. Meniscofemoral ligaments are straight bands of collagen that attach to the posterior horn of lateral meniscus and lateral part of medial femoral condyle [
Six hundred and three knee MRI examinations performed at our hospital during the period 2010-2011. Exclusion criteria include the patients with limitation on diagnosis due to motion artifacts and with imaging findings of PCL and lateral meniscus (LM) pathology. The remaining five hundred knee MRI exams were included in this retrospective study. The age of the patients ranged from 29 to 73 years (mean age 46 years). The patients were admitted for MRI exam either for chronic knee pain or after trauma.
All patients underwent MRI exams that were performed at 1 Tesla scanner (
For the interpretation of MRI examination we paid special attention to coronal and sagittal PD-WI sequence and sagittal T2-WI sequence. The two ligaments, Humphrey and Wrisberg, were observed as a thin, linear band, with low MR signal intensity on coronal images anteriorly or posteriorly to PCL, respectively. On the sagittal images aMFL had a low MR signal, dot-like appearance located anterior to PCL and pMFL with the same appearance leaning posterior to PCL.
The incidence of appearance, the different proportions in males and females, the MR sign and the occurrence were recorded.
Ethical approval for this study was not obtained due to the fact that this is a retrospective study and was not needed.
From 603 knee MR examinations, 103 were excluded. The incidence of MFLs was evaluated in the remaining 500 knee MRIs. The pMFL or Wrisberg ligament was present in a very high percentage, 322 patients (64,4%), (Figure
Coronal (a) PD-W image in which pMFL is demonstrating as a thick band and sagittal (b) PD-W image as a dot-like with low signal intensity posteriorly to posterior cruciate ligament (PCL) (white arrow).
On the contrary, aMFL was present in a smaller number of patients, 59 patients (11,8%) (Figure
Coronal (a) PD-W image in which aMFL is depicted as a thick band and in sagittal (b) PD-W image as a dot-like with low signal intensity anteriorly to PCL (white arrow).
Both anterior and posterior meniscofemoral ligaments were present in 81 patients (37%) (Figure
Incidence of appearance of ligament of Wrisberg and ligament of Humphrey in male and female patients.
aMFL | pMFL | aMFL + pMFL | |
---|---|---|---|
Male | 40 | 240 | 44 |
Female | 19 | 82 | 37 |
Incidence of appearance in different age groups.
Age group | aMFL | pMFL | aMFL + pMFL | Absent |
---|---|---|---|---|
20–30 y | 17 | 132 | 24 | 1 |
31–40 y | 13 | 57 | 29 | 2 |
41–50 y | 16 | 77 | 16 | 2 |
51–60 y | 8 | 33 | 8 | 10 |
>60 y | 5 | 23 | 4 | 23 |
39 years old female who admitted to our hospital for chronic pain. Consecutive (a) (b) coronal PD-W image evaluate both aMFL and pMFL as thick bands with low signal intensity anteriorly and posteriorly, respectively, to PCL (white cycle).
31 years old weekend football player, male, admitted to our hospital for medial meniscus tear. Consecutive (a) (b) coronal T2-W image demonstrating only the pMFL as a thick band with low signal intensity posteriorly to PCL. No fluid was present. MR examination was negative for meniscal tear (white arrow).
45 years old aerobic dancer, female, admitted to our hospital for trauma. Coronal STIR image demonstrating a very thick band with low signal intensity posteriorly to PCL, a large pMFL which plays the role of PCL (white arrow).
The Wrisberg ligament was thicker than the Humphrey ligament. It was depicted with clarity at the coronal sections. On the other hand, Humphrey ligament was thinner and better visualized on sagittal images.
The anatomy, the function, and the imaging of the MFLs are a major issue among anatomists, orthopedics, and radiologists. The meniscofemoral ligaments connect the posterior horn of lateral meniscus with the lateral part of medial femoral condyle [
Embryological studies in human and animal knees proposed that MFL starts from posterior horn of lateral meniscus as a single band. The appearance of single or double MFL is due to the position of the PCL. Based on this evidence, different hypothesis was made for the variants which could present a meniscofemoral ligament [
Anterior meniscofemoral ligament extents between the posterior portion of the posterior horn of the lateral meniscus and the femur, in the 10 o’clock position in a left knee, adjacent to the articular cartilage. Posterior meniscofemoral ligament leaning also between the anterior portion of the posterior horn on the lateral meniscus but at the femur it inserts at the medial part of the intercondylar notch near to insertion of the posteromedial band of the posterior cruciate ligament. This is the reason why fibers of the pMFL and PCL are sometimes intermingle [
The function of the aMFL and the pMFL is not clearly understood. We know that MFLs play an important role as stabilizers and protectors for the posterolateral femorotibial compartment. They try during knee motion to increase congruity between the mobile lateral meniscus and lateral femoral condyle. They also play a protective role for the posterior horn of the lateral meniscus. The MFL has a totally different function during knee extension and flexion due to the tension, which is applied on pMFL and aMFL, which is totally different. They have reciprocal and non-isometric tensioning pattern. The aMFL is taught during flexion and lax during extension that is in contrast to the function of the pMFL. It is taut during extension and lax during flexion. The aMFL has a supplementary role to the anterior band of posterior cruciate ligament in contrast with the pMFL which supplements the function of the posterior band of the PCL [
Imaging is adding important information regarding incidence of appearance. Several authors have shown, most through anatomic studies, the high prevalence of one of or both of MFLs. Anatomic studies, such as by Kusayama et al. and Amadi et al., demonstrate a very high incidence of 100%, thus other studies, such as Amis et al., a smaller incidence of 93% [
Each meniscofemoral ligament was separately evaluated. The incidence of pMFL was higher than incidence of aMFL in all studies. Cho et al. visualized the ligament of Wrisberg in 84% of cases, Lee et al. 80%, and the smallest incidence was by Erbagci et al. 42% [
We further divided the respective cohort regarding the sex of patients. The pMFL was present in 240 males, (74,6%) but fewer females, 82 patients (25,4%). Although Erbagci et al., visualized pMFL in a significant smaller cohort of 100 MRI knee examinations in 22 (52%) male patients and 20 (48%) females, the percentage of appearance is almost in accordance [
The aMFL was present in 40 males (67,8%), number disproportion higher than that of females 19 patients (32,2%). Amadi et al. visualized aMFL in 4 (33%) male patients and 8 (67%) females, which is in disagreement with our study [
Both MFLs were present at Moran et al. 28% and Lee et al. 1% [
We observed that the Wrisberg ligament was thicker than Humphrey ligament. It was depicted with clarity at the coronal sections. On the other hand, Humphrey ligament was thinner and better visualized on sagittal images. Lee et al. reached the same conclusion [
In this study the incidence and appearance of meniscofemoral ligaments has been presented for different age groups. Gupte et al. and Cho et al. have proposed that the incidence is higher in younger patients, which is in totally agreement with our series [
The present study has limitations. The retrospective nature in the study design does not allow any arthroscopic or surgical correlations.
The purpose of the present study was to give an overview of the radiologic prospective of the aMFL and pMFL. Degenerative cause might be able to explain the higher incidence in younger patients. The relatively large cohort of patients can contribute to the better knowledge of radiologic anatomy of meniscofemoral ligament and avert misdiagnosis of the aMFL and pMFL as loose bodies or PCL pathology.