Incidence and significance of demonstrating the meniscofemoral ligament on MRI

MRI study of the cruciate ligaments and menisco-femoral ligaments of the knee

PURPOSE

It has been argued that the meniscus-femoral ligaments disappear with age. We therefore analyzed the presence of the meniscus-femoral ligaments, in MRI.

MATERIALS AND METHODS

We measured the PCL, ACL and MFL, noting their presence or absence in 120 Knee MRIs, 51 in women and 69 in men. All knees underwent MRI in the coronal, sagittal and axial planes. T1 and T2 weighted sequences were obtained. A descriptive statistical study of all the variables was carried out, and a comparative study was performed between sexes, sides and age groups.

RESULTS

The MFLp was more frequent, found in 67 (55.8%) cases, than the MFLa, in 36 (30%) cases, and both together were present in 27 (22.5%) knees. We found a strong correlation between ACL length and PCL length (p = 0.001), we found no correlation between the presence of the posterior MFL either with age (p = 0.307) or with sex (p = 0.779) or side (p = 0.733). We also found no relationship between the presence of the anterior MFL and age (p = 0.553), or sex (p = 0.913), or laterality (p = 0.082).

CONCLUSION

We found a strong correlation between ACL length and PCL length. In our study, the presence of the posterior MFL was more frequent, being present in 55.68%, while the anterior MFL was found in 30% of the knees. We did not observe that the presence of LMF decreases with age.

Attachment Type, Thickness, and Volume of the Posterior Meniscofemoral Ligament and Meniscal Pathology

Several studies have investigated the relationship between the thickness of the posterior meniscofemoral ligament (pMFL) and the presence of a discoid meniscus. We investigated the correlation between meniscal pathology and anatomic features of pMFL such as attachment type, thickness, and volume. We retrospectively evaluated 191 patients who underwent knee MRI. MR images were reviewed to assess the attachment type of the pMFL on the medial femoral condyle (high vs. low), the thickness of the pMFL, and the presence of a meniscal tear or a discoid meniscus. The pMFL volume was quantified by using three-dimensional (3D) segmentation software. The relationship between the frequency of medial or lateral meniscal tear and anatomic features of pMFL were analyzed using Chi-square, Fisher's exact, or Mann-Whitney U test. High type pMFLs had significantly greater thickness and volume than low type pMFLs (p < 0.001). Patients with degenerative lateral meniscal tear had significantly higher thickness and volume of the pMFL than patients with intact lateral meniscus (p < 0.05). The pMFL thickness and volume were not significantly related to traumatic lateral meniscal tear, medial meniscal tear, and discoid meniscus. High type pMFLs tended to be thicker and larger than low type pMFLs and higher thickness and volume of the pMFL was significantly related to the degenerative lateral meniscal tear. However, the attachment type of the pMFL itself was not significantly related to the lateral meniscal tear as well as the medial meniscal tear.

Prevalence, Biomechanics, and Pathologies of the Meniscofemoral Ligaments: A Systematic Review

Purpose

To systematically review the literature to examine current understanding of the meniscofemoral ligaments (MFLs), their function, their importance in clinical management, and known anatomical variants.

Methods

A systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines using PubMed, EMBASE, and Cochrane databases. Studies were included if they reported on the biomechanical, radiographic, or arthroscopic evaluation of human MFLs, or if they reported on an anatomical variant. These were then categorized as cadaveric, radiographic, or clinical. Biomechanical, radiographic, patient-reported, and functional outcomes data were recorded.

Results

Forty-seven studies were included in the qualitative analysis, and 26 of them were included in the quantitative analysis. Of these, there were 15 cadaveric, 3 arthroscopic, and 9 radiographic studies that reported on the prevalence of MFLs. Overall, when looking at all modalities, the presence of either the anterior or posterior MFL (aMFL, pMFL) has been noted to be 70.8%, with it being the aMFL 17.4% and the pMFL 40.6%. The presence of both ligaments occurs in approximately 17.6% of individuals. Eleven reported on mean MFL length and thickness. When evaluating mean length in both men and women, the aMFL has been reported between 21.6 and 28.3 mm and the pMFL length in this population is between 23.4 and 31.2 mm. Five reported on cross-sectional area. Nine additional papers report anatomical variants.

Conclusions

This review shows that there continues to be a variable incidence of MFLs reported in the literature, but our understanding of their function continues to broaden. A growing number of anatomic and biomechanical studies have demonstrated the importance of the MFLs in supporting knee stability. Specifically, the MFLs serve an important role in protecting the lateral meniscus and augmenting the function of the posterior cruciate ligament.

Clinical Relevance

Our findings will aid the clinician in both identifying and treating pathologies of the meniscofemoral ligaments.

Radiological Comparison of Meniscofemoral Ligaments in Patients with Intact and Ruptured Anterior Cruciate Ligament

Background: Evaluating concomitant injury in patients with anterior cruciate ligament (ACL) rupture is important for predicting long-term results. Meniscofemoral ligament (MFL) rupture has been observed in patients with anterior cruciate ligament rupture in arthroscopic evaluation for ruptured ACL. Objectives: The objective of this study was to investigate the concomitant meniscofemoral ligaments injury in patients with anterior cruciate ligament ruptures via magnetic resonance imaging (MRI). Methods: A total of 200 patients (with ruptured ACL, n = 100; with intact ACL, n = 100) were retrospectively evaluated via MRI. In the group with ruptured ACL; the patients who were diagnosed as having noncontact ACL injuries and had undergone primary ACL reconstructions were included. The control group included 100 patients with suspected ACL rupture (from a similar injury mechanism) and whose MRI revealed an intact ACL. In the group with ruptured ACL, the time from injury to MRI was evaluated. A comparison of the presence of anterior MFL (aMFL) and posterior MFL (pMFL) between the two groups was evaluated. Results: In the ACL ruptured group, a significantly lower presence of aMFL or pMFL was observed compared to the control group (P = 0.001). The time from injury to MRI was significantly higher in the patients with absent MFL defined in MRI relative to the other groups (P = 0.001). Conclusions: We observed absence of MFLs (aMFL and pMFL) in a significant majority of patients with ruptured ACLs. Furthermore, we found a significant relationship between the time from injury to MRI and absence of MFL in the ruptured ACL group.

Clinical Anatomy of the Anterior Meniscofemoral Ligament of Humphrey: An Original MRI Study, Meta-analysis, and Systematic Review

Background:

The anterior meniscofemoral ligament (aMFL) of Humphrey is an anatomically variable fibrous band of connective tissue that attaches between the lateral aspect of the medial femoral condyle and posterior horn of the lateral meniscus, running posterior to the anterior cruciate ligament and anterior to the posterior cruciate ligament (PCL). The presence of an intact aMFL may contribute to stabilization of the lateral compartment of the knee joint.

Purpose:

The original magnetic resonance imaging (MRI) arm of this study aimed to assess the aMFL incidence among Polish patients. The goal of the systematic review and meta-analysis was to review the literature discussing the clinical anatomy of the aMFL and provide data on its prevalence. It was hypothesized that significant heterogeneity exists within the published literature.

Study Design:

Cross-sectional study and systematic review; Level of evidence, 3.

Methods:

A retrospective investigation was performed on the MRI scans of 100 knees (52 right, 48 left) of Polish patients. Scans were randomly selected from a database of MRI examinations performed in 2019. For the meta-analysis, major online databases were queried for data on the aMFL, and 2 authors independently assessed and extracted data from all included studies. A quality assessment of the included articles was performed using the Anatomical Quality Assessment tool.

Results:

In the MRI arm of this study, the aMFL was found in 62 of the 100 lower limbs. The meta-analysis included 41 studies with a total of 4220 limbs. The aMFL was present in 55.5% (95% CI, 45.5%-65.3%) of cases. Arthroscopic studies yielded the highest prevalence (82.3% [95% CI, 36.6%-100.0%]); of MRI studies, the highest prevalence was at 3.0-T strength (51.0% [95% CI, 13.3%-88.2%]).

Conclusion:

Significant variability in the prevalence of the aMFL was found in the literature. More emphasis should be placed on the clinical relevance of injuries to the aMFL because of its significant role in the function of the knee. It is important to be aware that, because of the anatomy of the aMFL, the ligament can also function to support a torn PCL.

Clinical Anatomy of the Posterior Meniscofemoral Ligament of Wrisberg: An Original MRI Study, Meta-analysis, and Systematic Review

Background

The posterior meniscofemoral ligament (pMFL) of Wrisberg attaches to the posterior horn of the lateral meniscus and the lateral intercondylar aspect of the medial femoral condyle and passes posteriorly to the posterior cruciate ligament (PCL). The pMFL plays a role in recovery after PCL injuries and offers stability to the lateral meniscus, promoting normal knee function.

Purpose/Hypothesis

The aim of the magnetic resonance imaging (MRI) arm of this study was to evaluate the prevalence of the pMFL in Polish patients. The purpose of the systematic review and meta-analysis was to evaluate the clinical relevance of the pMFL in knee surgery. It was hypothesized that extensive variability exists in reports on the prevalence, function, and clinical significance of the pMFL.

Study Design

Cross-sectional study and systematic review; Level of evidence, 3.

Methods

A retrospective MRI investigation was conducted on 100 randomly selected lower limbs of Polish patients (56 male, 44 female) performed in 2019 to determine the prevalence of the pMFL. Additionally, an extensive literature search of major online databases was performed to evaluate all reported data on the pMFL. Assessments of article eligibility and data extraction were completed independently by 2 reviewers, and all disagreements were resolved via a consensus. A quality assessment of the included articles was performed using the Anatomical Quality Assessment tool.

Results

In the MRI arm of this study, the pMFL was observed in 73 of the 100 limbs. In the meta-analysis, 47 studies were included, totaling 4940 lower limbs. The pooled prevalence of the pMFL was found to be 70.4% (95% CI, 63.4%-76.9%); the mean length was 27.7 mm (95% CI, 24.8-30.5 mm) and the mean widths were 4.5, 6.1, and 4.1 mm for the meniscal and femoral attachments and midportion, respectively. The mean pMFL thickness was 2.3 mm (95% CI, 1.8-2.7 mm).

Conclusion

Despite the variability in the literature, the pMFL was found to be a prevalent and large anatomic structure in the knee joint. The shared features of this ligament with the PCL necessitate the consideration of its value in planning and performing arthroscopic procedures of the knee.

Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI

OBJECTIVES

To quantify the morphological correlation between the posterior cruciate ligament (PCL) and the meniscofemoral ligaments (MFLs), to propose normal ranges for different age populations, and to define guidelines for correct identification and differentiation of MFLs in routine MRI.

METHODS

Three hundred forty-two subjects were included retrospectively and subdivided into five age groups. Morphometrics of the PCL and the MFLs were measured on standard MRI in the sagittal, coronal, and axial planes. Student's t test, Mann-Whitney U test, and ANOVA and Kruskal-Wallis tests with Bonferroni correction were used for comparison.

RESULTS

The MFLs did not vary significantly between sexes (p > 0.05) or in those older than 10 years (p > 0.05). Longitudinal MFL growth is completed before age 11 years, with cross-sectional area (CSA) increasing until age 20. The CSA of the PCL was significantly (p = 0.028) larger in knees without a pMFL (Mdn = 39.7 mm2) than with a pMFL (Mdn = 35.4 mm2). MFLs were more often detected on sagittal than coronal images.

CONCLUSIONS

This study describes the morphometric relation between the PCL and the MFLs on routine MRI. When reporting imaging findings in preparation for arthroscopic knee surgery, evaluation of MFLs, first in the sagittal and then the coronal plane, will achieve the best results.

KEY POINTS

• The MFLs and the PCL have distinct morphological patterns throughout life. • These patterns show intimate anatomical relationships and a potential biomechanical impact. • Those patterns and relationships can be quantified with MRI. • A correlation exists between age and morphometrics of the MFLs. • Recommendations for correct identification of the MFLs are provided.

Does high location and thickness of the Wrisberg ligament affect discoid lateral meniscus tear type based on peripheral detachment?

BACKGROUND

The aim of this study was to evaluate the relationship between discoid lateral meniscus (DLM) types based on peripheral detachment and anatomic features of Wrisberg ligament (WL) such as location and thickness based on magnetic resonance image (MRI).

METHODS

A total of 322 knees in 292 patients were reviewed. Patients were divided into four DLM types according to peripheral detachment: no shift (type 1), anterocentral shift (type 2), posterocentral shift (type 3) and central shift (type 4). We reviewed all MRI concentrating on the presence, location (high or low location), running angle, thickness of WL, and WL/posterior cruciate ligament (PCL) thickness ratio. The relationship between DLM types and anatomic features of WL were analyzed using one-way analysis of variance and chi-square test.

RESULTS

According to DLM types based on peripheral detachment, 149 knees were type 1, 38 were type 2, 79 were type 3, and 56 were type 4. Among the 322 knees, 302 (93.8%) had WL on MRI. In DLM patients, type 3 showed a statistically significant (P<0.001) relationship with high location of WL. In addition, type 3 had significantly larger (P<0.0001) running angle of WL, thicker (P<0.0001) WL, and higher (P<0.0001) WL/PCL ratio compared to other types.

CONCLUSION

A high location and thick WL are related to posterocentral shift type of DLM based on peripheral detachment. Based on our results, the high location and thick WL might provide information to surgeons in predicting the direction of peripheral detachment in symptomatic DLM patients.

The Meniscofemoral Ligament Mimicking a Lateral Meniscus Tear

A 58-year-old male patient who had developed left knee pain with a history of trauma was referred to our hospital. Physical examination and further examination by magnetic resonance imaging revealed results that closely resemble a horizontal tear of the lateral meniscus and a tear of the medial meniscus. Arthroscopically, we found a cord-like structure originating from the posterior 1/3 portion of the lateral meniscus and passing obliquely toward the medial femoral condyle in front of the posterior cruciate ligament without a tear of the lateral meniscus. In this report, we describe a rare case of anterior meniscofemoral ligament that was clearly seen on arthroscopy and mimicked a meniscal tear, which is also known as a pseudo-tear of the meniscus.

3-Tesla MRI: Beneficial visualization of the meniscofemoral ligaments?

BACKGROUND

Recent investigations have confirmed an important stabilizing and protective function of the meniscofemoral ligaments (MFLs) to the knee joint and suggest a clinical relevance. Concerning their incidences, however, there have been discrepancies between data acquired from cadaveric studies and MRI data using 0.3- to 1.5-Tesla field strengths probably due to lower resolution. This study aims to investigate whether imaging with 3-Tesla magnetic resonance imaging (3-T MRI) is beneficial in gaining information regarding the ligaments' incidence, length, width and anatomic variation.

METHODS

3-T MRI images of 448 patients (224 males, 224 females, with, respectively, 32 patients of each sex in the age groups: 0-20, 21-30, 31-40, 41-50, 51-60, 61-70, >70years) were retrospectively reviewed. The influence of the parameters 'sex' and 'age' was determined.

RESULTS

Whereas 71% of the patients had at least one MFL, 22% had an anterior MFL (aMFL), 53% had a posterior MFL (pMFL) and five percent had coexisting ligaments. The pMFLs were more likely to be present in female patients (P<0.05) but if so, they were longer in the males (P<0.05). The pMFL was categorized according to its insertion on the medial femoral condyle.

CONCLUSIONS

3-T MRI enables an excellent illustration of the anatomic variations of pMFLs. By modifying an anatomic classification for radiological use we measured lengths and widths of the MFLs without any difficulties. Despite its increased resolution, 3-T MRI lends no diagnostic benefit in visualizing the course of the aMFL or filigree coexisting ligaments as compared to MRI at lower field strengths.

Comparison of clinical, MRI and arthroscopic assessments of chronic ACL injuries, meniscal tears and cartilage defects

PURPOSE

The aim of this study was to compare the accuracy of clinical examination to that of MRI evaluated by two independent radiologists for the diagnosis of meniscal tears and chronic anterior cruciate ligament injuries and to assess the MRI accuracy in the diagnosis of cartilage defects.

METHODS

Seventy-six consecutive patients with suspected intra-articular knee pathology were prospectively evaluated by objective examination, 1.5 T MRI, re-examined by trained radiologist and arthroscopy. Accuracy, sensitivity, specificity, positive predictive value and negative predictive value were calculated. Agreement analysis with kappa (К) coefficient values was performed for meniscal and ACL tears.

RESULTS

No differences were found between diagnostic accuracy of clinical examination, the first and second MRI reports in diagnosis of medial meniscus (84 vs 96 vs 97 %) and anterior cruciate ligament injuries (93 vs 78 vs 89 %). For the lateral meniscal tears, the accuracy of the second radiologist was significantly higher than those of the first (96 vs 75 %; p < 0.01) and clinical examination (96 vs 86 %; p = 0.02). High diagnostic values were obtained for the diagnosis of full-thickness chondral defects with sensitivity of 100 %, specificity of 95 % and accuracy of 95 %.

CONCLUSION

Clinical and MRI evaluations have no differences in the diagnosis of medial meniscus and anterior cruciate ligament injuries. A trained radiologist obtained better sensitivity, specificity and accuracy in the diagnosis of lateral meniscus. 1.5 T MRI does not represent the technique of choice in the evaluation of chondral defect but demonstrated high diagnostic accuracy for detection of full-thickness chondral defects.

LEVEL OF EVIDENCE

Diagnostic prospective study, Level II.

Magnetic resonance evaluation of the knee in children and adolescents with achondroplasia

BACKGROUND

Achondroplasia is the most common form of skeletal dysplasia. Although the radiographic features are well described, MRI features of the knee in achondroplasia have not been reported.

OBJECTIVE

To describe common MRI characteristics of the knee joint in symptomatic children and adolescents with achondroplasia.

MATERIALS AND METHODS

We retrospectively evaluated 10 knee MRI examinations in 8 children and young adults (age range 11-20 years, mean 16.3 years) with achondroplasia. We measured modified Insall-Salvati index, knee flexion angle, anterior cruciate ligament (ACL)-Blumensaat line angle, ACL-tibial angle, posterior cruciate ligament (PCL) angle, intercondylar notch width index, and intercondylar notch depth index. We compared our findings with an age- and gender-matched control group of 20 children (age range 15-18 years; mean 16 years) with normal knee MRIs.

RESULTS

All 10 knees in the achondroplasia group had discoid lateral meniscus; 8 meniscal tears were identified. Patella baja was present in half of the study cases. Greater knee flexion and increased ACL-Blumensaat line and PCL angles were seen in all achondroplasia knees. ACL-tibial angle was similar in the study and in the control group. Children with achondroplasia had deeper A-shape femoral notches that extended more anteriorly than those seen in the control group. MRI findings were confirmed in all seven knees with arthroscopic correlation.

CONCLUSION

Discoid lateral meniscus, often with tear, is a consistent feature in knee MRIs of symptomatic children and adolescents with achondroplasia. Other findings include patella baja, knee flexion, deep A-shape intercondylar notch, increased ACL-Blumensaat line angle and taut PCL.

Meniscal injuries and imaging the postoperative meniscus

Meniscal injuries are common. Magnetic resonance imaging is considered the imaging modality of choice in diagnosing meniscal pathologic conditions in the nonoperative knee. Meniscal-preserving surgery is becoming more frequent, with a resultant increase in postoperative meniscal imaging, which is particularly challenging for the reporting radiologist. This article provides a review of the anatomy, pathologic conditions, and diagnostic pitfalls of meniscal injury, with a synopsis of the issues faced with postoperative meniscal imaging.

Anterior and posterior meniscofemoral ligaments: MRI evaluation

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.

Contribution of the meniscofemoral ligament as a restraint to the posterior tibial translation in a porcine knee

The meniscofemoral ligament (MFL) is a major structure in the posterior aspect of the porcine knee together with the posterior cruciate ligament (PCL). While the porcine knee is a frequently used animal model for biomechanical evaluation of PCL reconstruction techniques, the contribution of the MFL to stability of the porcine knee is not well understood. The purpose of this study is (1) to evaluate the kinematics of the knee after sequential cutting of the PCL and MFL and (2) to determine the in situ forces of the PCL and MFL in response to a posterior tibial load of 89 N using the robotic/universal force-moment sensor system from 15 degrees to 90 degrees of knee flexion. Ten porcine knees were used in this study. The magnitude of posterior tibial translation under a posterior tibial load was significantly increased (P < 0.01) after sequential transection of the PCL and the MFL at each testing angle compared to the intact condition. The in situ force of the PCL was highest at 60 degrees of flexion (82.3 +/- 8.6 N) and lowest at 15 degrees of flexion (45.1 +/- 15.9 N). The in situ force of the MFL was highest at 15 degrees of flexion (24.3 +/- 6.5 N) and lowest at 90 degrees of flexion (12.9 +/- 10.5 N). The findings in this study revealed a biomechanical contribution of the MFL as the secondary restraint to the posterior tibial translation in conjunction with the PCL especially near full extension.

Magnetic resonance imaging of the meniscus

Magnetic resonance imaging has evolved into a highly accurate modality in detecting meniscal injuries and provides the essential anatomic detail to help guide treatment options in this age of meniscal preservation. Accurate interpretation requires a thorough understanding of meniscal anatomy and function, anatomic variants, technical factors, typical appearance of tear patterns on magnetic resonance imaging, associated ligamentous injuries, causes of misdiagnoses, and the importance of correlation with the clinical examination.

Signification of the unusual delineation of the anterior meniscofemoral ligament of Humphrey during knee arthro-CT

BACKGROUND

Meniscofemoral ligaments (MFLs) are recognized as stabilizing and protective structures for the posterolateral meniscocondylar compartment of the knee, and as secondary restraints to tibial posterior translation.

PURPOSE AND PATIENTS

We report the 64-row arthro-MDCT findings of 10 patients (8 males, 2 females; mean age 43.8 years) in which the anterior MFL of Humphrey (aMLF) was atypically well delineated by an unusual circumferential effusion of iodine contrast. We discuss a possible physiopathologic mechanism for this effusion, describe the MDCT anatomy of the aMLF and review the literature about the anatomy and physiology of the MFLs.

RESULTS

In each of our ten patients an unusual effusion of articular contrast was found delineating a posterior oblique ligamentar bundle, which was running in front of the posterior cruciate ligament (PCL). This bundle was best appreciated on posterior coronal oblique and sagital MPR views, and was recognized as the aMFL. The finding was associated with a partial tear of the tibial insertion of the posterior horn (PH) of the lateral meniscus (LM) in three patients, and with a partial (two cases) or subtotal (three cases) tear of the PCL in five patients. A swollen-probably oedematous-PCL was found in another patient and in the last case the anomaly was minimal and remained isolated. All patients were treated conservatively.

CONCLUSION

Since the aMFL inserts inferiorly into the posterior horn of the LM and runs in very close anatomic and functional relation with the PCL, we hypothesize that a trauma producing a tear in these structures may also occasionally sufficiently stretch the aMFL to produce a peripheral loosening allowing a circumferential effusion of opacified synovial fluid around the ligament. Our report offers the opportunity to illustrate the "in vivo" anatomy of the aMFL through original unpublished figures. It also contributes to reinforce the literature data concerning the potential fine mechanical role played by the LM-MFLs-PCL complex, in which the centrally located MFLs act laterally as stabilizing and protective structures for the posterolateral meniscocondylar compartment and medially as secondary restraints to tibial posterior translation.

MR imaging of the meniscus: review, current trends, and clinical implications

MR imaging is the preferred imaging modality for evaluating the meniscus. Overall, when strict criteria are followed, it is accurate in diagnosing meniscal tears in patients who have not had prior meniscal surgery. However, an accurate interpretation requires a through knowledge of the normal meniscal anatomy, common meniscal variants, and common diagnostic pitfalls. In this article, the author emphasizes the importance of describing meniscal tears properly and discusses treatment options. Diagnosing a recurrent tear is more complicated in patients who have had prior partial meniscal resection or repair, and the use of MR arthrography in this group of patients is discussed. Recent developments in areas such as 3 T and parallel imaging offer promise for accurate meniscal evaluation with even shorter scan times.

Meniscofemoral ligaments: patterns of tears and pseudotears of the menisci using cadaveric and clinical material

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 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 degrees . 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.

Posterior horn lateral meniscal tears simulating meniscofemoral ligament attachment in the setting of ACL tear: MRI findings

PURPOSE

We have noted apparent far lateral meniscal attachment of the meniscofemoral ligament (MFL) with an anterior cruciate ligament (ACL) tear. This study evaluates MFL attachment and association with posterior horn lateral meniscus (PHLM) tear.

MATERIALS AND METHODS

Nine months of knee arthroscopy reports were reviewed to classify the PHLM and ACL as torn or normal. After excluding those with prior knee surgery, MR images were reviewed by two radiologists to determine the number of images lateral to PCL, which showed the ligaments of Humphrey and Wrisberg visible as structures separate from the PHLM. Any patient with abnormal PHLM surface signal not continuous with the MFL was excluded. MRI findings were compared with arthroscopy using Student's t test and Fisher's exact test.

RESULTS

Of the 54 participants, 5 had PHLM tears and 49 were normal. Twenty-one had ACL tears; all those with an PHLM tear had an ACL tear. The ligament of Humphrey inserted on average 0.9 consecutive images lateral to the PCL without an PHLM tear and 4.7 with an PHLM tear; the ligament of Wrisberg inserted on average 3.0 consecutive images without an PHLM tear and 4.5 with an PHLM tear (slice thickness/gap = 3 mm/0.5 mm). There was a significant association between PHLM tear and number of images (p = 0.0028), and between ACL tear and this type of PHLM tear (p = 0.0064).

CONCLUSION

Apparent far lateral meniscal extension of a meniscofemoral ligament (greater than or equal to four images lateral to the PCL) should be considered as a possible PHLM tear, especially in the setting of an ACL tear.

A new symptomatic intra-articular cord-like structure associated with discoid meniscus

We introduce a new, not yet described cord-like structure of the knee of children associated with discoid or enlarged menisci. This structure was responsible for knee pathology (loss of extension) in 3 cases. The patients (5 to 8 years of age) complained of knee pain without skeletal abnormality or trauma. Magnetic resonance imaging revealed enlarged or discoid lateral menisci. The patients showed increasing limp with limited range of motion. Lack of extension was between 10 degrees and 45 degrees and continued under anesthesia. During arthroscopy, the menisci and the anterior and posterior cruciate ligaments (ACL, PCL) showed no abnormality other than the variant of the lateral meniscus described above. A tight cord-like structure was imposed, running laterally along the ACL. This cord-like structure was attached to the lateral femoral intercondylar area and the posterior horn region of the lateral meniscus in a sail-like shape. Two knees showed abnormal mobility of the lateral meniscus, tending to luxate. The ligamentous structure was cut stepwise lateral to the ACL, leaving the entire lateral meniscus undisturbed. Finally, full extension was achieved. Examination 7 to 27 months after surgery showed asymptomatic knees. This ligamentous structure is an important differential diagnosis to symptoms usually referred to as meniscus pathology. The appropriate treatment involves dissection. A loss of meniscal tissue followed by development of osteoarthritis can be prevented.

MR Imaging of the Meniscus: Review, Current Trends, and Clinical Implications

MR imaging is the preferred imaging modality for evaluating the meniscus. Overall, when strict criteria are followed, it is accurate in diagnosing meniscal tears in patients who have not had prior meniscal surgery. However, an accurate interpretation requires a through knowledge of the normal meniscal anatomy, common meniscal variants, and common diagnostic pitfalls. In this article, the author emphasizes the importance of describing meniscal tears properly and discusses treatment options. Diagnosing a recurrent tear is more complicated in patients who have had prior partial meniscal resection or repair, and the use of MR arthrography in this group of patients is discussed. Recent developments in areas such as 3 T and parallel imaging offer promise for accurate meniscal evaluation with even shorter scan times.

Arthroscopic appearances of the meniscofemoral ligaments: introducing the "meniscal tug test"

To evaluate the feasibility of identifying the anterior and posterior meniscofemoral ligaments (aMFL and pMFL, respectively) at arthroscopy, both visually and using the "meniscal tug test", which exploits the anatomical attachments of the posterior cruciate ligament (PCL) and MFLs. This is an observational type of study. Arthroscopy using anteromedial and anterolateral portals was performed in 68 knees in 68 patients (36 right, 32 left). The MFLs were identified using several anatomical cues, including their femoral and meniscal attachments, their obliquity relative to the PCL, and the meniscal tug test. Identification was classed as easy or hard by the operating surgeon. From 68 knees, the aMFL was seen and confirmed to be an MFL using the tug test in 60 (88%). Identification of the aMFL was classed as easy in 64 (94%), whilst the pMFL was easy to identify in only 6 (9%) of knees, of which 3 had a ruptured PCL. Thus, with the exception of PCL-deficient knees, it was felt that the meniscal "tug test" as applied in this study was not suitable for the pMFL. The study shows that identification of the aMFL is possible in most knees at arthroscopy, using the "tug test" and other anatomical cues. However, identification of the pMFL may require a posterior portal. A subgroup of PCL injuries in which the MFLs were intact was also observed. The "meniscal tug test" can be used in arthroscopic examinations of the PCL to distinguish between fibres of the true PCL from the MFLs, thus avoiding the misdiagnosis of partial versus complete PCL rupture. This will also aid studies examining the role of the MFLs in stabilising the PCL-deficient knee.

Meniscus-stabilizing function of the meniscofemoral ligament: experimental study of pig knee joints

PURPOSE

To demonstrate experimentally, with the use of pig knee joints, that the posterior meniscofemoral ligament (PML) stabilizes the lateral meniscus (LM).

METHODS

Amputated stumps of the knee joints of Yorkshire pigs, which are anatomically similar to human knee joints, were used. The PML was intact or was cut according to 1 of 6 different conditions: (1) intact PML with intact LM, (2) intact PML with a radial tear of the posterior horn of the LM, (3) intact PML with total lateral meniscectomy, (4) cut PML with intact LM, (5) cut PML with a radial tear of the posterior horn of the LM, and (6) cut PML with total lateral meniscectomy. Pressure-sensitive film was inserted beneath the lateral femoral condyle, an axial load of 150 kg was placed on the knee joint with a universal testing machine, and the pressed area and maximum and average pressures were measured with the Prescale Imaging Analysis System (Fujifilm Medical Systems, Stamford, CT).

RESULTS

With an intact PML, no difference was seen between the intact meniscus and the radial tear of the posterior horn of the LM in pressed area and maximum and average pressures. With a cut PML, pressure concentration, detected as significantly reduced pressed area and increased maximum and average pressures, was observed, regardless of the condition of the LM.

CONCLUSIONS

PML of the pig stabilized the LM under an axial load, and an intact PML yielded results similar to those observed in total lateral meniscectomy. Our findings suggest that posterior horn tears of the LM, which are rarely symptomatic, may be caused by stabilizing of the lateral meniscus by the PML against the load placed on the knee joint.

CLINICAL RELEVANCE

Findings suggest that the PML, lateral side, stabilizes the LM when the ligament is intact. Even when a tear of the meniscus occurs, no increased localized pressure areas appear on the meniscus; this may explain why these tears are rarely symptomatic.

Intra-articular ganglion arising from the meniscofemoral ligament of Humphrey

We present a case of an intra-articular ganglion of the knee arising from the anterior meniscofemoral ligament of Humphrey. The MR imaging and arthroscopic appearance of the lesion are illustrated.

A review of the function and biomechanics of the meniscofemoral ligaments

PURPOSE

The goal of this study was to review current knowledge on the anatomy, biomechanics, and functions of the meniscofemoral ligaments.

TYPE OF STUDY

Literature review.

METHODS

A systematic search of the literature spanning the past 2 centuries was performed. This revealed several anatomic and biomechanical studies, which were analyzed for the presence, incidence, function, and biomechanics of the meniscofemoral ligaments.

RESULTS

An analysis of 16 anatomic studies revealed that from 1,022 cadaveric knees examined, 931 (91.1%) had at least 1 meniscofemoral ligament; an anterior meniscofemoral ligament was present in 390 (48.2%) of specimens, and a posterior meniscofemoral ligament was present in 569 (70.4%). The 2 ligaments coexisted in 257 knees (31.8%). This high incidence might imply a functional role for these structures. Early theories on the function of these ligaments focused on their role as secondary restraints supplementing the posterior cruciate ligament. More recent hypotheses have concentrated on a role in guiding the motion of the lateral meniscus.

CONCLUSIONS

The contribution of the meniscofemoral ligaments in the prognosis and management of posterior cruciate ligament and meniscal injuries remains undetermined. An examination of the structure, properties, and function of the meniscofemoral ligaments reveals that more biomechanical and imaging research is required, together with clinical observations, on the consequences of rupture of these ligaments.

Meniscofemoral ligaments--structural and material properties

The meniscofemoral ligaments (MFLs) of 28 human cadaveric knees were studied to determine their incidence, structural and material properties. Using the Race-Amis casting method for measurement, the mean cross-sectional area for the anterior MFL (aMFL) was 14.7 mm(2) (+/-14.8mm(2)) whilst that of the posterior MFL (pMFL) was 20.9 mm(2) (+/-11.6mm(2)). The ligaments were isolated and tensile tested in a materials testing machine. The mean loads to failure were 300.5 N (+/-155.0 N) for the aMFL and 302.5 N (+/-157.9 N) for the pMFL, with elastic moduli of 281 (+/-239 MPa) and 227 MPa (+/-128 MPa), respectively. These significant anatomical and material properties suggest a function for the MFL in the biomechanics of the knee, and should be borne in mind when considering hypotheses on MFL function. Such hypotheses include roles for the ligaments in knee stability and guiding meniscal motion.