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

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.

Mechanoreceptors observed in a ligamentous structure between the posterior horn of the lateral meniscus and the anterior cruciate ligament

PURPOSE

A histological study of a structure between the posterior horn of the lateral meniscus and the anterior cruciate ligament.

METHODS

Bilateral fresh-frozen cadaveric knees of two male donors (age 71 and 76 years) with no history of prior knee injury were examined. All dissections were performed by one experienced orthopaedic surgeon. Haematoxylin and Eosin staining was used to reveal tissue morphology. Goldner trichrome staining was used to evaluate the connective tissue. S100 and PGP 9.5 labelling were used for immunohistochemical analysis.

RESULTS

In all cadaveric knees, a structure between the posterior horn of the lateral meniscus and the anterior cruciate ligament was identified. Histological analysis confirmed the ligamentous nature of this structure. Furthermore, Golgi tendon organs were observed within the ligamentous structure.

CONCLUSION

This is the first study showing the presence of mechanoreceptors within the ligamentous structure between the posterior horn of the lateral meniscus and the anterior cruciate ligament. The ligamentous structure could contribute to stability of the knee by providing proprioceptive input, while preservation of the ligamentous structure might ensure a better functional outcome after surgery.

Posterior cruciate ligament: Anatomy, femoral insertion and relationships with the anterior menisco-femoral ligament in 23 cadaver knees

BACKGROUND

Abundant anatomic descriptions exist of the posterior cruciate ligament (PCL) and menisco-femoral ligaments (MFLs). There is broad agreement that the PCL is composed of two bundles and inserts on the femur near the distal cartilage. However, a different configuration with a single bundle and a complex femoral insertion has been reported. The main objective of our cadaver study was to determine the number of anatomical bundles forming the PCL. We also described the insertion of the PCL and its relationships with the anterior menisco-femoral ligament (AMFL).

HYPOTHESIS

The PCL consists of a single ribbon-like bundle and inserts on the femur separately from the AMFL.

MATERIAL AND METHODS

We used 23 knees of fresh unembalmed cadavers, which we dissected under a microsurgery loupe. Inclusion criteria for the knees were freedom from trauma and scars. No age limits were set. The features of the PCL were studied using the clock method. Measurements were taken using callipers with a precision of 0.01mm.

RESULTS

No knees were excluded from the final analysis. Macroscopically, the PCL appeared as a single bundle forming a slender flat ribbon. With the knee flexed at 90°, the ligament footprint extended from 58min to 25min on the right and from 48min to 2min on the left. The femoral insertion of the AMFL started 2.07mm from the distal cartilage and masked the distal insertion of the PCL. After removal of the AMFL, the middle of the femoral insertion of the PCL started on average 5.99mm from the distal cartilaginous rim when the knee was flexed at 90°.

DISCUSSION

Our study confirms descriptions of the PCL as a single bundle shaped as a flat ribbon. The presence of the AMFL gives the appearance of a double bundle and partially masks the femoral insertion of the PCL, which is located further back relative to the distal joint cartilage.

LEVEL OF EVIDENCE IV

Experimental cadaver study.

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.

Posterior cruciate ligament is twisted and flat structure: new prospective on anatomical morphology

PURPOSE

This cadaveric study aimed to elucidate PCL morphology by observing the anatomical relationship with other structures and the fibre layers of the PCL in cross section for remnant preserving PCL reconstruction.

METHODS

Seventeen fresh-frozen cadaveric knees were studied, using the clock-face method to analyse the anatomical relationship between the PCL and Humphrey's ligament. The width and thickness of the PCL, Humphrey's and Wrisberg's ligaments were measured. The PCL was cut sharply perpendicular to the tibia shaft, and the fibre layers were observed in cross section.

RESULTS

The PCL was located between 12 and 4 o'clock in the right knee (8 and 12 o'clock in the left), while Humphrey's ligament was located between 2 and 4 o'clock in the right knee (8 and 10 o'clock in the left). Humphrey's ligament at femoral insertion, midsubstance and lateral meniscus insertion averaged 8.7 ± 2.3, 5.9 ± 2.1 and 6.1 ± 2.0 mm, respectively, while the thickness at each level averaged 2.0 ± 1.2, 1.6 ± 0.6 and 1.9 ± 0.6 mm. The width of the PCL at midsubstance and at medial meniscus level averaged 13.3 ± 2.0 and 11.0 ± 1.6 mm, respectively, while the thickness of the PCL averaged 5.4 ± 0.8 and 5.5 ± 1.4 mm. In cross section, multiple, interconnected layers were observed which could not be divided. The main layers at each level were aligned from the posterolateral to the anteromedial aspect and formed a C-shape at the medial meniscus level.

CONCLUSION

The PCL at midsubstance is flat. PCL appears as a twisted ribbon composed of many small fibres without clearly separate bundles. When remnant preserving PCL reconstruction is performed, it is necessary to take account of not only PCL morphology but also the ligaments of Humphrey and Wrisberg. These findings may affect the PCL footprint and the graft shape in the future remnant preserving PCL reconstruction.

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.