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

Open AccessPublished:November 26, 2021DOI:https://doi.org/10.1016/j.asmr.2021.09.006

      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.
      The knee is both the largest and most susceptible joint to injury in the body.
      An accurate and detailed understanding of knee anatomy, including its variants, is necessary to diagnose and treat the numerous pathologies of the knee. Many advances have been made to further elucidate the function of the complex network of ligaments, tendons, and menisci as they work in concert to stabilize the joint. While much is known about each of these structures’ contributory effects on knee biomechanics, our understanding is still evolving.
      As part of this complex network, there are several ligaments that span the femur and menisci. The medial meniscus is primarily connected to the femur via the deep medial ligament.
      • LaPrade R.F.
      • Engebretsen A.H.
      • Ly T.V.
      • Johansen S.
      • Wentorf F.A.
      • Engebretsen L.
      The anatomy of the medial part of the knee.
      The lateral meniscus is connected to the femur via 2 ligaments of variable incidence, the meniscofemoral ligaments (MFLs).
      • Humphry G.M.
      A treatise on the human skeleton, including the joints.
      • Arthur J.R.
      • Haglin J.M.
      • Makovicka J.L.
      • Chhabra A.
      Anatomy and biomechanics of the posterior cruciate ligament and their surgical implications.
      • Gupte C.M.
      • Bull A.M.J.
      • Thomas R. de W.
      • Amis A.A.
      A review of the function and biomechanics of the meniscofemoral ligaments.
      These ligaments are named in relation to the posterior cruciate ligament (PCL). The anterior meniscofemoral ligament (aMFL), also known as the ligament of Humphrey, has been shown to have a variable origin, with approximately 80% attaching distally to the posteromedial bundle of the PCL (depicted in Figs 1 and 2).
      • Humphry G.M.
      A treatise on the human skeleton, including the joints.
      ,
      • Anderson C.J.
      • Ziegler C.G.
      • Wijdicks C.A.
      • Engebretsen L.
      • LaPrade R.F.
      Arthroscopically pertinent anatomy of the anterolateral and posteromedial bundles of the posterior cruciate ligament.
      The posterior meniscofemoral ligament (pMFL), also known as the ligament of Wrisberg, originates directly proximal to the medial intercondylar ridge, proximal to the posteromedial bundle of the PCL.
      • Anderson C.J.
      • Ziegler C.G.
      • Wijdicks C.A.
      • Engebretsen L.
      • LaPrade R.F.
      Arthroscopically pertinent anatomy of the anterolateral and posteromedial bundles of the posterior cruciate ligament.
      Figure thumbnail gr1
      Fig 1Anterior and posterior illustrations of the right knee depicting the origin and insertion sites of the aMFL and pMFL in relation to the PCL and menisci. (ACL, anterior cruciate ligament; ALB, anterolateral bundle; aMFL, anterior meniscofemoral ligament; PCL, posterior cruciate ligament; PLB, posterolateral bundle; PMB, posteromedial bundle; pMFL, posterior meniscofemoral ligament;)
      Figure thumbnail gr2
      Fig 2Axial illustration of the knee depicting insertion sites of the meniscofemoral ligaments in relation to the PCL on the tibia. (ACL, anterior cruciate ligament; ALB, anterolateral bundle; PCL, posterior cruciate ligament; PMB, posteromedial bundle.)
      Extensive research has detailed the position and incidence of the MFLs.
      • Ranalletta M.
      • Rossi W.
      • Paterno M.
      • Brigatti N.A.
      • Ranalletta A.
      Incidence of the anterior meniscofemoral ligament: An arthroscopic study in anterior cruciate ligament-deficient knees.
      • Ramos L.A.
      • de Carvalho R.T.
      • Cohen M.
      • Abdalla R.J.
      Anatomic relation between the posterior cruciate ligament and the joint capsule.
      • Poynton A.
      • Moran C.J.
      • Moran R.
      • O'Brien M.
      The meniscofemoral ligaments influence lateral meniscal motion at the human knee joint.
      • Poynton A.R.
      • Javadpour S.M.
      • Finegan P.J.
      • O'Brien M.
      The meniscofemoral ligaments of the knee.
      • Park L.S.
      • Jacobson J.A.
      • Jamadar D.A.
      • Caoili E.
      • Kalume-Brigido M.
      • Wojtys E.
      Posterior horn lateral meniscal tears simulating meniscofemoral ligament attachment in the setting of ACL tear: MRI findings.
      • Park B.K.
      • Lee H.
      • Kim S.-T.
      • Yoon M.G.
      The meniscofemoral ligament mimicking a lateral meniscus tear.
      • Osti M.
      • Tschann P.
      • Künzel K.H.
      • Benedetto K.P.
      Posterolateral corner of the knee: Microsurgical analysis of anatomy and morphometry.
      • Oliveira H.C. de S.
      • Gali J.C.
      • Caetano E.B.
      Anatomical relationships between Wrisberg meniscofemoral and posterior cruciate ligament’s femoral insertions.
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      • Lee B.Y.
      • Jee W.H.
      • Kim J.M.
      • Kim B.S.
      • Choi K.H.
      Incidence and significance of demonstrating the meniscofemoral ligament on MRI.
      • Kusayama T.
      • Harner C.D.
      • Carlin G.J.
      • Xerogeanes J.W.
      • Smith B.A.
      Anatomical and biomechanical characteristics of human meniscofemoral ligaments.
      • Aggarwal P.
      • Pal A.
      • Ghosal A.
      • Datta I.
      • Banerjee B.
      A morphological and morphometric study on meniscofemoral ligaments of knee joint and its variations.
      • Bintoudi A.
      • Natsis K.
      • Tsitouridis I.
      Anterior and posterior meniscofemoral ligaments: MRI evaluation.
      However, a limited number of studies have proposed theories regarding their function.
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      • Forkel P.
      • Herbort M.
      • Sprenker F.
      • Metzlaff S.
      • Raschke M.
      • Petersen W.
      The biomechanical effect of a lateral meniscus posterior root tear with and without damage to the meniscofemoral ligament: Efficacy of different repair techniques.
      • Geeslin A.G.
      • Civitarese D.
      • Turnbull T.L.
      • Dornan G.J.
      • Fuso F.A.
      • LaPrade R.F.
      Influence of lateral meniscal posterior root avulsions and the meniscofemoral ligaments on tibiofemoral contact mechanics.
      • Hamada M.
      • Miyama T.
      • Nagayama Y.
      • Shino K.
      Repair of a torn medial meniscus with an anteromedial meniscofemoral ligament in an anterior cruciate ligament-injured knee.
      • Vahey T.N.
      • Bennett H.T.
      • Arrington L.E.
      • Shelbourne K.D.
      • Ng J.
      MR imaging of the knee: Pseudotear of the lateral meniscus caused by the meniscofemoral ligament.
      As their role in knee biomechanics continues to unfold, these structures have potential implications for the advancement of surgical intervention on the PCL and menisci. The purpose of this study was to systematically review the literature to examine current understanding of the MFLs, their function, their importance in clinical management, and known anatomical variants. We hypothesize that these ligaments have a variable incidence in the literature, with at least one being present in the majority of people, and that full understanding of their clinical significance is still evolving.

      Methods

      Institutional review board reviewed this study, and it was deemed to be exempt. This systematic review was conducted using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.
      • Moher D.
      • Liberati A.
      • Tetzlaff J.
      • Altman D.G.
      Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement.
      Two independent reviewers (D.G.D. and S.T.) conducted the initial literature search in December 2020 using PubMed, EMBASE, and Cochrane Central Register of Controlled Trials databases. A broad-based search was conducted to ensure no studies were missed using the following search terms: “meniscofemoral ligament” OR “meniscofemoral ligaments.” All searches were conducted using a date range from database inception to current time of search. Studies were included in the systematic review if (1) they reported biomechanical, radiographic, or arthroscopic evaluation of human meniscofemoral ligaments or (2) described an anatomical variant. Only full-text manuscripts written in the English language were included and no level of evidence restrictions were imposed. Technique articles, review articles, letters to the editor, animal studies, or studies not published in the English language were excluded. Case reports of unique anatomical variants were included.

       Statistical Analysis

      Studies were classified as either cadaveric, radiographic, or arthroscopic analyses. Papers were assessed for reporting prevalence of MFLs. These data were recorded as total number of specimens or patients, a single ligament, aMFL only, total number of aMFLs, pMFL only, total number of pMFLs, and presence of both ligaments. Biomechanical data regarding length, width, and cross-sectional area also were collected if reported. Descriptive statistics (mean, range, percentage, and standard deviation) were performed using Microsoft Excel (Redmond, WA).

      Results

      The search results were reviewed independently by 2 authors (D.G.D. and S.T.) to select studies for inclusion in the review. After removal of duplicates, the initial keyword literature search produced a total of 219 references. Ninety-five studies were identified for inclusion from the literature search based on appropriateness of title and abstract content. These 95 studies then underwent full-text review to confirm appropriateness for inclusion. The reference list and text of each latter manuscript was cross-referenced to identify any additional studies related to the study topic not previously found. Following full-text review and cross-referencing, 47 studies met all criteria for inclusion and were included in the review.
      • Ranalletta M.
      • Rossi W.
      • Paterno M.
      • Brigatti N.A.
      • Ranalletta A.
      Incidence of the anterior meniscofemoral ligament: An arthroscopic study in anterior cruciate ligament-deficient knees.
      • Ramos L.A.
      • de Carvalho R.T.
      • Cohen M.
      • Abdalla R.J.
      Anatomic relation between the posterior cruciate ligament and the joint capsule.
      • Poynton A.
      • Moran C.J.
      • Moran R.
      • O'Brien M.
      The meniscofemoral ligaments influence lateral meniscal motion at the human knee joint.
      • Poynton A.R.
      • Javadpour S.M.
      • Finegan P.J.
      • O'Brien M.
      The meniscofemoral ligaments of the knee.
      • Park L.S.
      • Jacobson J.A.
      • Jamadar D.A.
      • Caoili E.
      • Kalume-Brigido M.
      • Wojtys E.
      Posterior horn lateral meniscal tears simulating meniscofemoral ligament attachment in the setting of ACL tear: MRI findings.
      • Park B.K.
      • Lee H.
      • Kim S.-T.
      • Yoon M.G.
      The meniscofemoral ligament mimicking a lateral meniscus tear.
      • Osti M.
      • Tschann P.
      • Künzel K.H.
      • Benedetto K.P.
      Posterolateral corner of the knee: Microsurgical analysis of anatomy and morphometry.
      • Oliveira H.C. de S.
      • Gali J.C.
      • Caetano E.B.
      Anatomical relationships between Wrisberg meniscofemoral and posterior cruciate ligament’s femoral insertions.
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      • Lee B.Y.
      • Jee W.H.
      • Kim J.M.
      • Kim B.S.
      • Choi K.H.
      Incidence and significance of demonstrating the meniscofemoral ligament on MRI.
      • Kusayama T.
      • Harner C.D.
      • Carlin G.J.
      • Xerogeanes J.W.
      • Smith B.A.
      Anatomical and biomechanical characteristics of human meniscofemoral ligaments.
      • Aggarwal P.
      • Pal A.
      • Ghosal A.
      • Datta I.
      • Banerjee B.
      A morphological and morphometric study on meniscofemoral ligaments of knee joint and its variations.
      • Bintoudi A.
      • Natsis K.
      • Tsitouridis I.
      Anterior and posterior meniscofemoral ligaments: MRI evaluation.
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      • Forkel P.
      • Herbort M.
      • Sprenker F.
      • Metzlaff S.
      • Raschke M.
      • Petersen W.
      The biomechanical effect of a lateral meniscus posterior root tear with and without damage to the meniscofemoral ligament: Efficacy of different repair techniques.
      • Geeslin A.G.
      • Civitarese D.
      • Turnbull T.L.
      • Dornan G.J.
      • Fuso F.A.
      • LaPrade R.F.
      Influence of lateral meniscal posterior root avulsions and the meniscofemoral ligaments on tibiofemoral contact mechanics.
      • Hamada M.
      • Miyama T.
      • Nagayama Y.
      • Shino K.
      Repair of a torn medial meniscus with an anteromedial meniscofemoral ligament in an anterior cruciate ligament-injured knee.
      • Vahey T.N.
      • Bennett H.T.
      • Arrington L.E.
      • Shelbourne K.D.
      • Ng J.
      MR imaging of the knee: Pseudotear of the lateral meniscus caused by the meniscofemoral ligament.
      ,
      • Ahn J.H.
      • Wang J.H.
      • Kim D.U.
      • Lee D.K.
      • Kim J.H.
      Does high location and thickness of the Wrisberg ligament affect discoid lateral meniscus tear type based on peripheral detachment?.
      • Amadi H.O.
      • Gupte C.M.
      • Lie D.T.T.
      • McDermott I.D.
      • Amis A.A.
      • Bull A.M.J.
      A biomechanical study of the meniscofemoral ligaments and their contribution to contact pressure reduction in the knee.
      • Anderson A.F.
      • Awh M.H.
      • Anderson C.N.
      The anterior meniscofemoral ligament of the medial meniscus: Case series.
      • Brantigan O.C.
      • Voshell A.F.
      Ligaments of the knee joint; the relationship of the ligament of Humphry to the ligament of Wrisberg.
      • Cho J.M.
      • Suh J.S.
      • Na J.B.
      • et al.
      Variations in meniscofemoral ligaments at anatomical study and MR imaging.
      • Cross M.B.
      • Raphael B.S.
      • Maak T.G.
      • Plaskos C.
      • Egidy C.C.
      • Pearle A.D.
      Characterization of the orientation and isometry of Humphrey’s ligament.
      • Ebrecht J.
      • Krasny A.
      • Hartmann D.M.
      • Rückbeil M.V.
      • Ritz T.
      • Prescher A.
      3-Tesla MRI: Beneficial visualization of the meniscofemoral ligaments?.
      • Erbagci H.
      • Yildirim H.
      • Kizilkan N.
      • Gümüsburun E.
      An MRI study of the meniscofemoral and transverse ligaments of the knee.
      • Gupte C.M.
      • Smith A.
      • McDermott I.D.
      • Bull A.M.J.
      • Thomas R.D.
      • Amis A.A.
      Meniscofemoral ligaments revisited.
      • Gupte C.M.
      • Bull A.M.J.
      • Atkinson H.D.
      • Thomas R.D.
      • Strachan R.K.
      • Amis A.A.
      Arthroscopic appearances of the meniscofemoral ligaments: Introducing the “meniscal tug test.
      • Gupte C.M.
      • Shaerf D.A.
      • Sandison A.
      • Bull A.M.J.
      • Amis A.A.
      Neural structures within human meniscofemoral ligaments: A cadaveric study.
      • Gupte C.M.
      • Smith A.
      • Jamieson N.
      • Bull A.M.J.
      • Thomas R.D.W.
      • Amis A.A.
      Meniscofemoral ligaments—Structural and material properties.
      • Han S.H.
      • Kim D.I.
      • Choi S.G.
      • Lee J.H.
      • Kim Y.S.
      The posterior meniscofemoral ligament: Morphologic study and anatomic classification.
      • Harner C.D.
      • Livesay G.A.
      • Kashiwaguchi S.
      • Fujie H.
      • Choi N.Y.
      • Woo S.L.
      Comparative study of the size and shape of human anterior and posterior cruciate ligaments.
      • Heller L.
      • Langman J.
      The menisco-femoral ligaments of the human knee.
      • Kim E.Y.
      • Choi S.H.
      • Ahn J.H.
      • Kwon J.W.
      Atypically thick and high location of the Wrisberg ligament in patients with a complete lateral discoid meniscus.
      • Kim J.E.
      • Choi S.H.
      Is the location of the Wrisberg ligament related to frequent complete discoid lateral meniscus tear?.
      • Kim Y.M.
      • Joo Y.B.
      Anteromedial meniscofemoral ligament of the anterior horn of the medial meniscus: clinical, magnetic resonance imaging, and arthroscopic features.
      • Kim Y.-M.
      • Joo Y.-B.
      • Yeon K.-W.
      • Lee K.-Y.
      Anterolateral meniscofemoral ligament of the lateral meniscus.
      • Moran C.J.
      • Poynton A.R.
      • Moran R.
      • Brien M.O.
      Analysis of meniscofemoral ligament tension during knee motion.
      • Röhrich S.
      • Kainberger F.
      • Hirtler L.
      Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI.
      • Rosenberg T.D.
      • Paulos L.E.
      • Parker R.D.
      • Harner C.D.
      • Gurley W.D.
      Discoid lateral meniscus: Case report of arthroscopic attachment of a symptomatic Wrisberg-ligament type.
      • Silva A.
      • Sampaio R.
      Anterior lateral meniscofemoral ligament with congenital absence of the ACL.
      • Soejima T.
      • Murakami H.
      • Tanaka N.
      • Nagata K.
      Anteromedial meniscofemoral ligament.
      • Sonin A.
      • Reister J.A.
      Intra-articular ganglion arising from the meniscofemoral ligament of Humphrey.
      • Tanifuji K.
      • Tajima G.
      • Yan J.
      • et al.
      Three-dimensional computed tomography confirmed that the meniscal root attachments and meniscofemoral ligaments are morphologically consistent.
      • Trinh J.M.
      • De Verbizier J.
      • Lecocq Texeira S.
      • et al.
      Imaging appearance and prevalence of the anteromedial meniscofemoral ligament: A potential pitfall to anterior cruciate ligament analysis on MRI.
      • Watanabe A.T.
      • Carter B.C.
      • Teitelbaum G.P.
      • Bradley W.G.
      Common pitfalls in magnetic resonance imaging of the knee.
      • Yamamoto M.
      • Hirohata K.
      Anatomical study on the menisco-femoral ligaments of the knee.
      After each step of the review process, any disagreement on inclusion of a study was resolved by discussion and agreement between the two reviewers. If consensus could not be reached, then inclusion was decided by the senior author (A.C.). A flow diagram outlining the selection process is found in Figure 3. Of these 47 studies, 26 were subsequently included for quantitative review based on study design to allow for simplified organization and improved comparison between similar studies.
      • Ranalletta M.
      • Rossi W.
      • Paterno M.
      • Brigatti N.A.
      • Ranalletta A.
      Incidence of the anterior meniscofemoral ligament: An arthroscopic study in anterior cruciate ligament-deficient knees.
      ,
      • Ramos L.A.
      • de Carvalho R.T.
      • Cohen M.
      • Abdalla R.J.
      Anatomic relation between the posterior cruciate ligament and the joint capsule.
      ,
      • Poynton A.R.
      • Javadpour S.M.
      • Finegan P.J.
      • O'Brien M.
      The meniscofemoral ligaments of the knee.
      ,
      • Osti M.
      • Tschann P.
      • Künzel K.H.
      • Benedetto K.P.
      Posterolateral corner of the knee: Microsurgical analysis of anatomy and morphometry.
      ,
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      • Lee B.Y.
      • Jee W.H.
      • Kim J.M.
      • Kim B.S.
      • Choi K.H.
      Incidence and significance of demonstrating the meniscofemoral ligament on MRI.
      • Kusayama T.
      • Harner C.D.
      • Carlin G.J.
      • Xerogeanes J.W.
      • Smith B.A.
      Anatomical and biomechanical characteristics of human meniscofemoral ligaments.
      • Aggarwal P.
      • Pal A.
      • Ghosal A.
      • Datta I.
      • Banerjee B.
      A morphological and morphometric study on meniscofemoral ligaments of knee joint and its variations.
      • Bintoudi A.
      • Natsis K.
      • Tsitouridis I.
      Anterior and posterior meniscofemoral ligaments: MRI evaluation.
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      ,
      • Vahey T.N.
      • Bennett H.T.
      • Arrington L.E.
      • Shelbourne K.D.
      • Ng J.
      MR imaging of the knee: Pseudotear of the lateral meniscus caused by the meniscofemoral ligament.
      ,
      • Amadi H.O.
      • Gupte C.M.
      • Lie D.T.T.
      • McDermott I.D.
      • Amis A.A.
      • Bull A.M.J.
      A biomechanical study of the meniscofemoral ligaments and their contribution to contact pressure reduction in the knee.
      ,
      • Brantigan O.C.
      • Voshell A.F.
      Ligaments of the knee joint; the relationship of the ligament of Humphry to the ligament of Wrisberg.
      ,
      • Cho J.M.
      • Suh J.S.
      • Na J.B.
      • et al.
      Variations in meniscofemoral ligaments at anatomical study and MR imaging.
      ,
      • Ebrecht J.
      • Krasny A.
      • Hartmann D.M.
      • Rückbeil M.V.
      • Ritz T.
      • Prescher A.
      3-Tesla MRI: Beneficial visualization of the meniscofemoral ligaments?.
      • Erbagci H.
      • Yildirim H.
      • Kizilkan N.
      • Gümüsburun E.
      An MRI study of the meniscofemoral and transverse ligaments of the knee.
      • Gupte C.M.
      • Smith A.
      • McDermott I.D.
      • Bull A.M.J.
      • Thomas R.D.
      • Amis A.A.
      Meniscofemoral ligaments revisited.
      • Gupte C.M.
      • Bull A.M.J.
      • Atkinson H.D.
      • Thomas R.D.
      • Strachan R.K.
      • Amis A.A.
      Arthroscopic appearances of the meniscofemoral ligaments: Introducing the “meniscal tug test.
      ,
      • Gupte C.M.
      • Smith A.
      • Jamieson N.
      • Bull A.M.J.
      • Thomas R.D.W.
      • Amis A.A.
      Meniscofemoral ligaments—Structural and material properties.
      • Han S.H.
      • Kim D.I.
      • Choi S.G.
      • Lee J.H.
      • Kim Y.S.
      The posterior meniscofemoral ligament: Morphologic study and anatomic classification.
      • Harner C.D.
      • Livesay G.A.
      • Kashiwaguchi S.
      • Fujie H.
      • Choi N.Y.
      • Woo S.L.
      Comparative study of the size and shape of human anterior and posterior cruciate ligaments.
      • Heller L.
      • Langman J.
      The menisco-femoral ligaments of the human knee.
      ,
      • Röhrich S.
      • Kainberger F.
      • Hirtler L.
      Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI.
      ,
      • Tanifuji K.
      • Tajima G.
      • Yan J.
      • et al.
      Three-dimensional computed tomography confirmed that the meniscal root attachments and meniscofemoral ligaments are morphologically consistent.
      ,
      • Watanabe A.T.
      • Carter B.C.
      • Teitelbaum G.P.
      • Bradley W.G.
      Common pitfalls in magnetic resonance imaging of the knee.
      ,
      • Yamamoto M.
      • Hirohata K.
      Anatomical study on the menisco-femoral ligaments of the knee.
      All studies describing anatomical variants were summarized.
      Figure thumbnail gr3
      Fig 3Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flowsheet demonstrating literature review process.

       Prevalence

      The prevalence of aMFL, pMFL, or both has been variably reported in the literature as seen in Table 1.
      • Ranalletta M.
      • Rossi W.
      • Paterno M.
      • Brigatti N.A.
      • Ranalletta A.
      Incidence of the anterior meniscofemoral ligament: An arthroscopic study in anterior cruciate ligament-deficient knees.
      ,
      • Ramos L.A.
      • de Carvalho R.T.
      • Cohen M.
      • Abdalla R.J.
      Anatomic relation between the posterior cruciate ligament and the joint capsule.
      ,
      • Poynton A.R.
      • Javadpour S.M.
      • Finegan P.J.
      • O'Brien M.
      The meniscofemoral ligaments of the knee.
      ,
      • Osti M.
      • Tschann P.
      • Künzel K.H.
      • Benedetto K.P.
      Posterolateral corner of the knee: Microsurgical analysis of anatomy and morphometry.
      ,
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      • Lee B.Y.
      • Jee W.H.
      • Kim J.M.
      • Kim B.S.
      • Choi K.H.
      Incidence and significance of demonstrating the meniscofemoral ligament on MRI.
      • Kusayama T.
      • Harner C.D.
      • Carlin G.J.
      • Xerogeanes J.W.
      • Smith B.A.
      Anatomical and biomechanical characteristics of human meniscofemoral ligaments.
      • Aggarwal P.
      • Pal A.
      • Ghosal A.
      • Datta I.
      • Banerjee B.
      A morphological and morphometric study on meniscofemoral ligaments of knee joint and its variations.
      • Bintoudi A.
      • Natsis K.
      • Tsitouridis I.
      Anterior and posterior meniscofemoral ligaments: MRI evaluation.
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      ,
      • Vahey T.N.
      • Bennett H.T.
      • Arrington L.E.
      • Shelbourne K.D.
      • Ng J.
      MR imaging of the knee: Pseudotear of the lateral meniscus caused by the meniscofemoral ligament.
      ,
      • Amadi H.O.
      • Gupte C.M.
      • Lie D.T.T.
      • McDermott I.D.
      • Amis A.A.
      • Bull A.M.J.
      A biomechanical study of the meniscofemoral ligaments and their contribution to contact pressure reduction in the knee.
      ,
      • Brantigan O.C.
      • Voshell A.F.
      Ligaments of the knee joint; the relationship of the ligament of Humphry to the ligament of Wrisberg.
      ,
      • Cho J.M.
      • Suh J.S.
      • Na J.B.
      • et al.
      Variations in meniscofemoral ligaments at anatomical study and MR imaging.
      ,
      • Ebrecht J.
      • Krasny A.
      • Hartmann D.M.
      • Rückbeil M.V.
      • Ritz T.
      • Prescher A.
      3-Tesla MRI: Beneficial visualization of the meniscofemoral ligaments?.
      • Erbagci H.
      • Yildirim H.
      • Kizilkan N.
      • Gümüsburun E.
      An MRI study of the meniscofemoral and transverse ligaments of the knee.
      • Gupte C.M.
      • Smith A.
      • McDermott I.D.
      • Bull A.M.J.
      • Thomas R.D.
      • Amis A.A.
      Meniscofemoral ligaments revisited.
      • Gupte C.M.
      • Bull A.M.J.
      • Atkinson H.D.
      • Thomas R.D.
      • Strachan R.K.
      • Amis A.A.
      Arthroscopic appearances of the meniscofemoral ligaments: Introducing the “meniscal tug test.
      ,
      • Gupte C.M.
      • Smith A.
      • Jamieson N.
      • Bull A.M.J.
      • Thomas R.D.W.
      • Amis A.A.
      Meniscofemoral ligaments—Structural and material properties.
      • Han S.H.
      • Kim D.I.
      • Choi S.G.
      • Lee J.H.
      • Kim Y.S.
      The posterior meniscofemoral ligament: Morphologic study and anatomic classification.
      • Harner C.D.
      • Livesay G.A.
      • Kashiwaguchi S.
      • Fujie H.
      • Choi N.Y.
      • Woo S.L.
      Comparative study of the size and shape of human anterior and posterior cruciate ligaments.
      • Heller L.
      • Langman J.
      The menisco-femoral ligaments of the human knee.
      ,
      • Röhrich S.
      • Kainberger F.
      • Hirtler L.
      Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI.
      ,
      • Tanifuji K.
      • Tajima G.
      • Yan J.
      • et al.
      Three-dimensional computed tomography confirmed that the meniscal root attachments and meniscofemoral ligaments are morphologically consistent.
      ,
      • Watanabe A.T.
      • Carter B.C.
      • Teitelbaum G.P.
      • Bradley W.G.
      Common pitfalls in magnetic resonance imaging of the knee.
      ,
      • Yamamoto M.
      • Hirohata K.
      Anatomical study on the menisco-femoral ligaments of the knee.
      Several different modalities have been used to evaluate its prevalence, including cadaveric dissection, arthroscopy, and magnetic resonance imaging (MRI). Of these, there were 15 cadaveric, 3 arthroscopic, and 9 radiographic studies that reported on the prevalence of MFLs. Most of the reported prevalence data cited in the literature is derived from cadaveric dissection studies, although these present a wide range of values.
      • Ramos L.A.
      • de Carvalho R.T.
      • Cohen M.
      • Abdalla R.J.
      Anatomic relation between the posterior cruciate ligament and the joint capsule.
      ,
      • Poynton A.R.
      • Javadpour S.M.
      • Finegan P.J.
      • O'Brien M.
      The meniscofemoral ligaments of the knee.
      ,
      • Osti M.
      • Tschann P.
      • Künzel K.H.
      • Benedetto K.P.
      Posterolateral corner of the knee: Microsurgical analysis of anatomy and morphometry.
      ,
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      ,
      • Kusayama T.
      • Harner C.D.
      • Carlin G.J.
      • Xerogeanes J.W.
      • Smith B.A.
      Anatomical and biomechanical characteristics of human meniscofemoral ligaments.
      ,
      • Aggarwal P.
      • Pal A.
      • Ghosal A.
      • Datta I.
      • Banerjee B.
      A morphological and morphometric study on meniscofemoral ligaments of knee joint and its variations.
      ,
      • Amadi H.O.
      • Gupte C.M.
      • Lie D.T.T.
      • McDermott I.D.
      • Amis A.A.
      • Bull A.M.J.
      A biomechanical study of the meniscofemoral ligaments and their contribution to contact pressure reduction in the knee.
      ,
      • Brantigan O.C.
      • Voshell A.F.
      Ligaments of the knee joint; the relationship of the ligament of Humphry to the ligament of Wrisberg.
      ,
      • Gupte C.M.
      • Bull A.M.J.
      • Atkinson H.D.
      • Thomas R.D.
      • Strachan R.K.
      • Amis A.A.
      Arthroscopic appearances of the meniscofemoral ligaments: Introducing the “meniscal tug test.
      ,
      • Gupte C.M.
      • Shaerf D.A.
      • Sandison A.
      • Bull A.M.J.
      • Amis A.A.
      Neural structures within human meniscofemoral ligaments: A cadaveric study.
      ,
      • Han S.H.
      • Kim D.I.
      • Choi S.G.
      • Lee J.H.
      • Kim Y.S.
      The posterior meniscofemoral ligament: Morphologic study and anatomic classification.
      • Harner C.D.
      • Livesay G.A.
      • Kashiwaguchi S.
      • Fujie H.
      • Choi N.Y.
      • Woo S.L.
      Comparative study of the size and shape of human anterior and posterior cruciate ligaments.
      • Heller L.
      • Langman J.
      The menisco-femoral ligaments of the human knee.
      ,
      • Tanifuji K.
      • Tajima G.
      • Yan J.
      • et al.
      Three-dimensional computed tomography confirmed that the meniscal root attachments and meniscofemoral ligaments are morphologically consistent.
      ,
      • Yamamoto M.
      • Hirohata K.
      Anatomical study on the menisco-femoral ligaments of the knee.
      The presence of either the aMFL or pMFL has ranged from 16.7-100%, with it being only the aMFL 10% to 40% of the time and only the pMFL 24% to 86% of the time. The presence of both ligaments has varied from 1% to 64.3%. Among the 3 arthroscopic studies of these structures, the presence of either the aMFL or pMFL has been seen >94% of the time, with it being the aMFL 88.2% and the pMFL 14.7%.
      • Ranalletta M.
      • Rossi W.
      • Paterno M.
      • Brigatti N.A.
      • Ranalletta A.
      Incidence of the anterior meniscofemoral ligament: An arthroscopic study in anterior cruciate ligament-deficient knees.
      ,
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      ,
      • Gupte C.M.
      • Bull A.M.J.
      • Atkinson H.D.
      • Thomas R.D.
      • Strachan R.K.
      • Amis A.A.
      Arthroscopic appearances of the meniscofemoral ligaments: Introducing the “meniscal tug test.
      The presence of both ligaments has been seen 8.8% of the time. Finally, in the 9 included MRI studies, the presence of either the aMFL or pMFL has ranged from 21.1% to 100%, with it being the aMFL 2.9% to 32.5% and the pMFL 11.9% to 78.3%.
      • Lee B.Y.
      • Jee W.H.
      • Kim J.M.
      • Kim B.S.
      • Choi K.H.
      Incidence and significance of demonstrating the meniscofemoral ligament on MRI.
      ,
      • Bintoudi A.
      • Natsis K.
      • Tsitouridis I.
      Anterior and posterior meniscofemoral ligaments: MRI evaluation.
      ,
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      ,
      • Vahey T.N.
      • Bennett H.T.
      • Arrington L.E.
      • Shelbourne K.D.
      • Ng J.
      MR imaging of the knee: Pseudotear of the lateral meniscus caused by the meniscofemoral ligament.
      ,
      • Cho J.M.
      • Suh J.S.
      • Na J.B.
      • et al.
      Variations in meniscofemoral ligaments at anatomical study and MR imaging.
      ,
      • Ebrecht J.
      • Krasny A.
      • Hartmann D.M.
      • Rückbeil M.V.
      • Ritz T.
      • Prescher A.
      3-Tesla MRI: Beneficial visualization of the meniscofemoral ligaments?.
      ,
      • Erbagci H.
      • Yildirim H.
      • Kizilkan N.
      • Gümüsburun E.
      An MRI study of the meniscofemoral and transverse ligaments of the knee.
      ,
      • Röhrich S.
      • Kainberger F.
      • Hirtler L.
      Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI.
      ,
      • Watanabe A.T.
      • Carter B.C.
      • Teitelbaum G.P.
      • Bradley W.G.
      Common pitfalls in magnetic resonance imaging of the knee.
      The presence of both ligaments has varied from 1.2% to 47.4%. Overall, when we looked at all modalities, the cumulative mean of either the aMFL and/or pMFL being present was found to be 70.8%.
      • Ranalletta M.
      • Rossi W.
      • Paterno M.
      • Brigatti N.A.
      • Ranalletta A.
      Incidence of the anterior meniscofemoral ligament: An arthroscopic study in anterior cruciate ligament-deficient knees.
      ,
      • Ramos L.A.
      • de Carvalho R.T.
      • Cohen M.
      • Abdalla R.J.
      Anatomic relation between the posterior cruciate ligament and the joint capsule.
      ,
      • Poynton A.R.
      • Javadpour S.M.
      • Finegan P.J.
      • O'Brien M.
      The meniscofemoral ligaments of the knee.
      ,
      • Osti M.
      • Tschann P.
      • Künzel K.H.
      • Benedetto K.P.
      Posterolateral corner of the knee: Microsurgical analysis of anatomy and morphometry.
      ,
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      • Lee B.Y.
      • Jee W.H.
      • Kim J.M.
      • Kim B.S.
      • Choi K.H.
      Incidence and significance of demonstrating the meniscofemoral ligament on MRI.
      • Kusayama T.
      • Harner C.D.
      • Carlin G.J.
      • Xerogeanes J.W.
      • Smith B.A.
      Anatomical and biomechanical characteristics of human meniscofemoral ligaments.
      • Aggarwal P.
      • Pal A.
      • Ghosal A.
      • Datta I.
      • Banerjee B.
      A morphological and morphometric study on meniscofemoral ligaments of knee joint and its variations.
      • Bintoudi A.
      • Natsis K.
      • Tsitouridis I.
      Anterior and posterior meniscofemoral ligaments: MRI evaluation.
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      ,
      • Vahey T.N.
      • Bennett H.T.
      • Arrington L.E.
      • Shelbourne K.D.
      • Ng J.
      MR imaging of the knee: Pseudotear of the lateral meniscus caused by the meniscofemoral ligament.
      ,
      • Amadi H.O.
      • Gupte C.M.
      • Lie D.T.T.
      • McDermott I.D.
      • Amis A.A.
      • Bull A.M.J.
      A biomechanical study of the meniscofemoral ligaments and their contribution to contact pressure reduction in the knee.
      ,
      • Brantigan O.C.
      • Voshell A.F.
      Ligaments of the knee joint; the relationship of the ligament of Humphry to the ligament of Wrisberg.
      ,
      • Cho J.M.
      • Suh J.S.
      • Na J.B.
      • et al.
      Variations in meniscofemoral ligaments at anatomical study and MR imaging.
      ,
      • Ebrecht J.
      • Krasny A.
      • Hartmann D.M.
      • Rückbeil M.V.
      • Ritz T.
      • Prescher A.
      3-Tesla MRI: Beneficial visualization of the meniscofemoral ligaments?.
      • Erbagci H.
      • Yildirim H.
      • Kizilkan N.
      • Gümüsburun E.
      An MRI study of the meniscofemoral and transverse ligaments of the knee.
      • Gupte C.M.
      • Smith A.
      • McDermott I.D.
      • Bull A.M.J.
      • Thomas R.D.
      • Amis A.A.
      Meniscofemoral ligaments revisited.
      • Gupte C.M.
      • Bull A.M.J.
      • Atkinson H.D.
      • Thomas R.D.
      • Strachan R.K.
      • Amis A.A.
      Arthroscopic appearances of the meniscofemoral ligaments: Introducing the “meniscal tug test.
      ,
      • Gupte C.M.
      • Smith A.
      • Jamieson N.
      • Bull A.M.J.
      • Thomas R.D.W.
      • Amis A.A.
      Meniscofemoral ligaments—Structural and material properties.
      • Han S.H.
      • Kim D.I.
      • Choi S.G.
      • Lee J.H.
      • Kim Y.S.
      The posterior meniscofemoral ligament: Morphologic study and anatomic classification.
      • Harner C.D.
      • Livesay G.A.
      • Kashiwaguchi S.
      • Fujie H.
      • Choi N.Y.
      • Woo S.L.
      Comparative study of the size and shape of human anterior and posterior cruciate ligaments.
      • Heller L.
      • Langman J.
      The menisco-femoral ligaments of the human knee.
      ,
      • Röhrich S.
      • Kainberger F.
      • Hirtler L.
      Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI.
      ,
      • Tanifuji K.
      • Tajima G.
      • Yan J.
      • et al.
      Three-dimensional computed tomography confirmed that the meniscal root attachments and meniscofemoral ligaments are morphologically consistent.
      ,
      • Watanabe A.T.
      • Carter B.C.
      • Teitelbaum G.P.
      • Bradley W.G.
      Common pitfalls in magnetic resonance imaging of the knee.
      ,
      • Yamamoto M.
      • Hirohata K.
      Anatomical study on the menisco-femoral ligaments of the knee.
      The presence of both ligaments occurs in approximately 17.6% of individuals.
      • Ranalletta M.
      • Rossi W.
      • Paterno M.
      • Brigatti N.A.
      • Ranalletta A.
      Incidence of the anterior meniscofemoral ligament: An arthroscopic study in anterior cruciate ligament-deficient knees.
      ,
      • Ramos L.A.
      • de Carvalho R.T.
      • Cohen M.
      • Abdalla R.J.
      Anatomic relation between the posterior cruciate ligament and the joint capsule.
      ,
      • Poynton A.R.
      • Javadpour S.M.
      • Finegan P.J.
      • O'Brien M.
      The meniscofemoral ligaments of the knee.
      ,
      • Osti M.
      • Tschann P.
      • Künzel K.H.
      • Benedetto K.P.
      Posterolateral corner of the knee: Microsurgical analysis of anatomy and morphometry.
      ,
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      • Lee B.Y.
      • Jee W.H.
      • Kim J.M.
      • Kim B.S.
      • Choi K.H.
      Incidence and significance of demonstrating the meniscofemoral ligament on MRI.
      • Kusayama T.
      • Harner C.D.
      • Carlin G.J.
      • Xerogeanes J.W.
      • Smith B.A.
      Anatomical and biomechanical characteristics of human meniscofemoral ligaments.
      • Aggarwal P.
      • Pal A.
      • Ghosal A.
      • Datta I.
      • Banerjee B.
      A morphological and morphometric study on meniscofemoral ligaments of knee joint and its variations.
      • Bintoudi A.
      • Natsis K.
      • Tsitouridis I.
      Anterior and posterior meniscofemoral ligaments: MRI evaluation.
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      ,
      • Vahey T.N.
      • Bennett H.T.
      • Arrington L.E.
      • Shelbourne K.D.
      • Ng J.
      MR imaging of the knee: Pseudotear of the lateral meniscus caused by the meniscofemoral ligament.
      ,
      • Amadi H.O.
      • Gupte C.M.
      • Lie D.T.T.
      • McDermott I.D.
      • Amis A.A.
      • Bull A.M.J.
      A biomechanical study of the meniscofemoral ligaments and their contribution to contact pressure reduction in the knee.
      ,
      • Brantigan O.C.
      • Voshell A.F.
      Ligaments of the knee joint; the relationship of the ligament of Humphry to the ligament of Wrisberg.
      ,
      • Cho J.M.
      • Suh J.S.
      • Na J.B.
      • et al.
      Variations in meniscofemoral ligaments at anatomical study and MR imaging.
      ,
      • Gupte C.M.
      • Smith A.
      • Jamieson N.
      • Bull A.M.J.
      • Thomas R.D.W.
      • Amis A.A.
      Meniscofemoral ligaments—Structural and material properties.
      • Han S.H.
      • Kim D.I.
      • Choi S.G.
      • Lee J.H.
      • Kim Y.S.
      The posterior meniscofemoral ligament: Morphologic study and anatomic classification.
      • Harner C.D.
      • Livesay G.A.
      • Kashiwaguchi S.
      • Fujie H.
      • Choi N.Y.
      • Woo S.L.
      Comparative study of the size and shape of human anterior and posterior cruciate ligaments.
      • Heller L.
      • Langman J.
      The menisco-femoral ligaments of the human knee.
      ,
      • Gupte C.M.
      • Smith A.
      • Jamieson N.
      • Bull A.M.J.
      • Thomas R.D.W.
      • Amis A.A.
      Meniscofemoral ligaments—Structural and material properties.
      • Han S.H.
      • Kim D.I.
      • Choi S.G.
      • Lee J.H.
      • Kim Y.S.
      The posterior meniscofemoral ligament: Morphologic study and anatomic classification.
      • Harner C.D.
      • Livesay G.A.
      • Kashiwaguchi S.
      • Fujie H.
      • Choi N.Y.
      • Woo S.L.
      Comparative study of the size and shape of human anterior and posterior cruciate ligaments.
      • Heller L.
      • Langman J.
      The menisco-femoral ligaments of the human knee.
      ,
      • Röhrich S.
      • Kainberger F.
      • Hirtler L.
      Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI.
      ,
      • Tanifuji K.
      • Tajima G.
      • Yan J.
      • et al.
      Three-dimensional computed tomography confirmed that the meniscal root attachments and meniscofemoral ligaments are morphologically consistent.
      ,
      • Watanabe A.T.
      • Carter B.C.
      • Teitelbaum G.P.
      • Bradley W.G.
      Common pitfalls in magnetic resonance imaging of the knee.
      ,
      • Yamamoto M.
      • Hirohata K.
      Anatomical study on the menisco-femoral ligaments of the knee.
      Table 1Summary of Reported Prevalence of MFLs in the Literature
      StudyNumber of Subjects/SpecimensSingle Ligament n, (%)aMFL Only

      n, (%)
      Total aMFL n, (%)pMFL Only

      n, (%)
      Total pMFL n, (%)Both n, (%)
      Cadaveric Dissection
       Brantigan and Voshell
      • Brantigan O.C.
      • Voshell A.F.
      Ligaments of the knee joint; the relationship of the ligament of Humphry to the ligament of Wrisberg.
      5050 (100)20 (40)23 (46)30 (60)33 (66)3 (6)
       Heller and Langman
      • Heller L.
      • Langman J.
      The menisco-femoral ligaments of the human knee.
      14099 (70.7)42 (30)50 (35.7)41 (29.3)49 (35)8 (5.7)
       Yamamoto and Hirohata
      • Yamamoto M.
      • Hirohata K.
      Anatomical study on the menisco-femoral ligaments of the knee.
      100100 (100)27 (27)76 (76)24 (24)73 (73)49 (49)
       Kusayama et al.
      • Kusayama T.
      • Harner C.D.
      • Carlin G.J.
      • Xerogeanes J.W.
      • Smith B.A.
      Anatomical and biomechanical characteristics of human meniscofemoral ligaments.
      2626 (100)6 (23.1)18 (69.2)8 (30.8)20 (76.9)12 (46.2)
       Harner et al.
      • Harner C.D.
      • Livesay G.A.
      • Kashiwaguchi S.
      • Fujie H.
      • Choi N.Y.
      • Woo S.L.
      Comparative study of the size and shape of human anterior and posterior cruciate ligaments.
      88 (100)2 (25)4 (50)4 (50)6 (75)2 (25)
       Poynton et al.
      • Poynton A.R.
      • Javadpour S.M.
      • Finegan P.J.
      • O'Brien M.
      The meniscofemoral ligaments of the knee.
      4242 (100)8 (19)35 (83.3)11 (26.2)38 (90.5)27 (64.3)
       Gupte et al.
      • Gupte C.M.
      • Smith A.
      • Jamieson N.
      • Bull A.M.J.
      • Thomas R.D.W.
      • Amis A.A.
      Meniscofemoral ligaments—Structural and material properties.
      2815 (53.6)7 (25)18 (64.3)8 (28.6)19 (67.9)11 (39.3)
       Gupte et al.
      • Gupte C.M.
      • Smith A.
      • McDermott I.D.
      • Bull A.M.J.
      • Thomas R.D.
      • Amis A.A.
      Meniscofemoral ligaments revisited.
      8478 (92.9)20 (23.8)62 (73.8)16 (19)58 (69)42 (50)
       Nagasaki et al.
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      305 (16.7)5 (16.7)5 (16.7)0 (0)0 (0)0 (0)
       Amadi et al.
      • Amadi H.O.
      • Gupte C.M.
      • Lie D.T.T.
      • McDermott I.D.
      • Amis A.A.
      • Bull A.M.J.
      A biomechanical study of the meniscofemoral ligaments and their contribution to contact pressure reduction in the knee.
      51 (20)1 (20)5 (100)0 (0)4 (80)4 (80)
       Ramos et al.
      • Ramos L.A.
      • de Carvalho R.T.
      • Cohen M.
      • Abdalla R.J.
      Anatomic relation between the posterior cruciate ligament and the joint capsule.
      30n/an/an/an/a12 (40)n/a
       Han et al.
      • Han S.H.
      • Kim D.I.
      • Choi S.G.
      • Lee J.H.
      • Kim Y.S.
      The posterior meniscofemoral ligament: Morphologic study and anatomic classification.
      10086 (86)0 (0)1 (1)86 (86)87 (87)1 (1)
       Osti et al.
      • Osti M.
      • Tschann P.
      • Künzel K.H.
      • Benedetto K.P.
      Posterolateral corner of the knee: Microsurgical analysis of anatomy and morphometry.
      30n/an/an/an/a25 (83.3)n/a
       Aggarwal et al.
      • Aggarwal P.
      • Pal A.
      • Ghosal A.
      • Datta I.
      • Banerjee B.
      A morphological and morphometric study on meniscofemoral ligaments of knee joint and its variations.
      3838 (100)4 (10.5)14 (36.8)24 (63.2)34 (89.5)10 (26.3)
       Tanifuji et al.
      • Tanifuji K.
      • Tajima G.
      • Yan J.
      • et al.
      Three-dimensional computed tomography confirmed that the meniscal root attachments and meniscofemoral ligaments are morphologically consistent.
      28n/an/a6 (21.4)n/a24 (85.7)5 (17.9)
      Arthroscopy
       Gupte et al.
      • Gupte C.M.
      • Bull A.M.J.
      • Atkinson H.D.
      • Thomas R.D.
      • Strachan R.K.
      • Amis A.A.
      Arthroscopic appearances of the meniscofemoral ligaments: Introducing the “meniscal tug test.
      6864 (94.1)60 (88.2)66 (97.1)10 (14.7)16 (23.5)6 (8.8)
       Nagasaki et al.
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      3832 (100)n/a14 (36.8)n/a27 (71.1)n/a
       Ranalletta et al.
      • Ranalletta M.
      • Rossi W.
      • Paterno M.
      • Brigatti N.A.
      • Ranalletta A.
      Incidence of the anterior meniscofemoral ligament: An arthroscopic study in anterior cruciate ligament-deficient knees.
      140n/an/a140 (100)n/an/an/a
      MRI
       Watanabe et al.
      • Watanabe A.T.
      • Carter B.C.
      • Teitelbaum G.P.
      • Bradley W.G.
      Common pitfalls in magnetic resonance imaging of the knee.
      200131 (65.5)65 (32.5)71 (35.5)66 (33)72 (36)6 (1.2)
       Vahey et al.
      • Vahey T.N.
      • Bennett H.T.
      • Arrington L.E.
      • Shelbourne K.D.
      • Ng J.
      MR imaging of the knee: Pseudotear of the lateral meniscus caused by the meniscofemoral ligament.
      10923 (21.1)10 (9.2)11 (10.1)13 (11.9)14 (12.8)1 (2.0)
       Cho et al.
      • Cho J.M.
      • Suh J.S.
      • Na J.B.
      • et al.
      Variations in meniscofemoral ligaments at anatomical study and MR imaging.
      10079 (79)3 (3)17 (17)76 (76)90 (90)14 (14)
       Lee et al.
      • Lee B.Y.
      • Jee W.H.
      • Kim J.M.
      • Kim B.S.
      • Choi K.H.
      Incidence and significance of demonstrating the meniscofemoral ligament on MRI.
      138112 (81.2)4 (2.9)6 (4.3)108 (78.3)110 (79.7)2 (1.4)
       Abreu et al.
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      4929 (59.2)5 (10.2)27 (55.1)24 (49.0)46 (93.9)22 (44.9)
       Bintoudi et al.
      • Bintoudi A.
      • Natsis K.
      • Tsitouridis I.
      Anterior and posterior meniscofemoral ligaments: MRI evaluation.
      500381 (76.2)59 (11.8)140 (28)322 (64.4)403 (80.6)81 (16.2)
       Erbagci et al.
      • Erbagci H.
      • Yildirim H.
      • Kizilkan N.
      • Gümüsburun E.
      An MRI study of the meniscofemoral and transverse ligaments of the knee.
      10082 (82)12 (12)40 (40)42 (42)70 (70)28 (28)
       Ebrecht et al.
      • Ebrecht J.
      • Krasny A.
      • Hartmann D.M.
      • Rückbeil M.V.
      • Ritz T.
      • Prescher A.
      3-Tesla MRI: Beneficial visualization of the meniscofemoral ligaments?.
      448294 (65.6)77 (17.2)97 (21.7)217 (48.4)237 (52.9)20 (4.5)
       Röhrich et al.
      • Röhrich S.
      • Kainberger F.
      • Hirtler L.
      Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI.
      342324 (100)79 (23.1)241 (70.6)82 (24)244 (71.3)162 (47.4)
      Overall totals30212,138 (70.8)526 (17.4)1,212 (40.1)1,227 (40.6)1,841 (60.9)531 (17.6)
      aMFL, anterior meniscofemoral ligament; MFL, meniscofemoral ligament; MRI, magnetic resonance imaging; n/a, not available; pMFL, posterior meniscofemoral ligament.

       Length, Width, and Cross-Sectional Area of aMFL and pMFL

      The mean aMFL and pMFL length and thickness was reported in several studies as seen in Table 2. When we evaluated the mean length in both men and women, the aMFL has been reported between 21.6 and 28.3 mm. The pMFL length in this population was between 23.4 and 31.2 mm. The length in both aMFL and pMFL has been reported as longer in men than women although not always statistically significant.
      Table 2Mean MFL Lengths and Thickness
      StudyMean aMFL Length, mm ± SDMean pMFL Length, mm ± SDMean aMFL Thickness, mm ± SDMean pMFL Thickness, mm ± SD
      Abreu et al.
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      n/an/a1.9 ± 0.61.8 ± 0.7
      Aggarwal et al.
      • Aggarwal P.
      • Pal A.
      • Ghosal A.
      • Datta I.
      • Banerjee B.
      A morphological and morphometric study on meniscofemoral ligaments of knee joint and its variations.
      25.7 ± 2.031.6 ± 4.94.9 ±0.74.9 ± 1.2
      Poynton et al.
      • Poynton A.R.
      • Javadpour S.M.
      • Finegan P.J.
      • O'Brien M.
      The meniscofemoral ligaments of the knee.
       Male27.1 ± 2.231.1 ± 2.5n/an/a
       Female24.4 ± 3.427.6 ± 3.7n/an/a
      Yamaoto and Hirohata
      • Yamamoto M.
      • Hirohata K.
      Anatomical study on the menisco-femoral ligaments of the knee.
      28.331.2n/an/a
      Candiollo and Gautero
      • Candiollo L.
      • Gautero G.
      Morphology and function of the menisco-femoral ligaments of the knee joint in man.
      21.623.4n/an/a
      Ebrecht et al.
      • Ebrecht J.
      • Krasny A.
      • Hartmann D.M.
      • Rückbeil M.V.
      • Ritz T.
      • Prescher A.
      3-Tesla MRI: Beneficial visualization of the meniscofemoral ligaments?.
       Malen/a28.2 ± 3.7n/a2.2 ± 1.3
       Femalen/a25.4 ± 3.2n/a2.3 ± 1.3
      Erbagci et al.
      • Erbagci H.
      • Yildirim H.
      • Kizilkan N.
      • Gümüsburun E.
      An MRI study of the meniscofemoral and transverse ligaments of the knee.
       Male11.1 ± 2.628.8 ± 5.52.5 ± 0.92.3 ± 1.2
       Female9.9 ± 4.825.6 ± 5.52.5 ± 1.02.3 ± 1.2
      Osti et al.
      • Osti M.
      • Tschann P.
      • Künzel K.H.
      • Benedetto K.P.
      Posterolateral corner of the knee: Microsurgical analysis of anatomy and morphometry.
      n/a23.8 ± 3.17n/an/a
      Röhrich et al.
      • Röhrich S.
      • Kainberger F.
      • Hirtler L.
      Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI.
      22 ± 328 ± 4n/an/a
      Total21.3 ±7.027.7 ± 2.93.0 ± 0.82.6 ± 1.2
      aMFL, anterior meniscofemoral ligament; MFL, meniscofemoral ligament; n/a, not available; pMFL; posterior meniscofemoral ligament; SD, standard deviation.
      When we evaluated mean thickness in both men and women, the aMFL has been reported between 1.9 ± 0.6 and 25.7 ± 2.0 mm. The pMFL length in this population was between 1.8 ± 0.7 and 31.6 ± 4.9 mm. The cross-sectional area of the aMFL and pMFL as reported in the literature can be seen in Table 3. The aMFL ranges from 2.2 ± 1.7 to 14.7 ± 14.8. The pMFL ranges from 3.3 ± 2.6 to 20.9 ± 11.6.
      Table 3Mean MFL Cross-Sectional Areas
      StudyMean aMFL CSA, mm2 ± SDMean pMFL CSA, mm2 ± SD
      Kusayama et al.
      • Kusayama T.
      • Harner C.D.
      • Carlin G.J.
      • Xerogeanes J.W.
      • Smith B.A.
      Anatomical and biomechanical characteristics of human meniscofemoral ligaments.
      7.8 ± 4.76.7 ± 4.1
      Gupte et al.
      • Gupte C.M.
      • Smith A.
      • Jamieson N.
      • Bull A.M.J.
      • Thomas R.D.W.
      • Amis A.A.
      Meniscofemoral ligaments—Structural and material properties.
      14.7 ± 14.820.9 ± 11.6
      Nagasaki et al.
      • Nagasaki S.
      • Ohkoshi Y.
      • Yamamoto K.
      • Ebata W.
      • Imabuchi R.
      • Nishiike J.
      The incidence and cross-sectional area of the meniscofemoral ligament.
      2.3 ± 1.27.5 ± 2.5
      Osti et al.
      • Osti M.
      • Tschann P.
      • Künzel K.H.
      • Benedetto K.P.
      Posterolateral corner of the knee: Microsurgical analysis of anatomy and morphometry.
      n/a3.62 ± 1.0
      Röhrich et al.
      • Röhrich S.
      • Kainberger F.
      • Hirtler L.
      Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI.
      2.2 ± 1.73.3 ± 2.6
      aMFL, anterior meniscofemoral ligament; CSA, cross-sectional area; MFL, meniscofemoral ligament; n/a, not available; pMFL; posterior meniscofemoral ligament; SD, standard deviation.

       Clinical Pathology

       Meniscofemoral Ligaments and Pseudotears of the Lateral Meniscus

      Investigations by of the aMFL and pMFL by Gupte et al.
      • Gupte C.M.
      • Smith A.
      • McDermott I.D.
      • Bull A.M.J.
      • Thomas R.D.
      • Amis A.A.
      Meniscofemoral ligaments revisited.
      and Poyton et al.
      • Poynton A.
      • Moran C.J.
      • Moran R.
      • O'Brien M.
      The meniscofemoral ligaments influence lateral meniscal motion at the human knee joint.
      have demonstrated an interplay between them and the posterior horn of the lateral meniscus during knee flexion and extension which has led to speculation that these ligaments may have a role meniscal pathology. Despite this relationship, Abreu et al.
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      found no association between presence of one or both MFLs and occurrence of medial or lateral meniscal tears.
      Given their intimacy with the menisci, MFLs have falsely been diagnosed as tears of the posterior horn of the lateral meniscus, or “pseudotears” on MRI with up to a 63% incidence.
      • Park B.K.
      • Lee H.
      • Kim S.-T.
      • Yoon M.G.
      The meniscofemoral ligament mimicking a lateral meniscus tear.
      ,
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      ,
      • Vahey T.N.
      • Bennett H.T.
      • Arrington L.E.
      • Shelbourne K.D.
      • Ng J.
      MR imaging of the knee: Pseudotear of the lateral meniscus caused by the meniscofemoral ligament.
      These pseudotears have particularly been found to have an oblique orientation from anterosuperior to posteroinferior and less commonly with a vertical orientation.
      • Abreu M.R.
      • Chung C.B.
      • Trudell D.
      • Resnick D.
      Meniscofemoral ligaments: Patterns of tears and pseudotears of the menisci using cadaveric and clinical material.
      ,
      • Vahey T.N.
      • Bennett H.T.
      • Arrington L.E.
      • Shelbourne K.D.
      • Ng J.
      MR imaging of the knee: Pseudotear of the lateral meniscus caused by the meniscofemoral ligament.

       Discoid Meniscus and pMFL Attachment

      In patients with complete discoid menisci, it has been noted that the pMFL has an increased thickness and presents with a higher riding attachment as compared with non-discoid menisci.
      • Ahn J.H.
      • Wang J.H.
      • Kim D.U.
      • Lee D.K.
      • Kim J.H.
      Does high location and thickness of the Wrisberg ligament affect discoid lateral meniscus tear type based on peripheral detachment?.
      ,
      • Kim E.Y.
      • Choi S.H.
      • Ahn J.H.
      • Kwon J.W.
      Atypically thick and high location of the Wrisberg ligament in patients with a complete lateral discoid meniscus.
      ,
      • Kim Y.M.
      • Joo Y.B.
      Anteromedial meniscofemoral ligament of the anterior horn of the medial meniscus: clinical, magnetic resonance imaging, and arthroscopic features.
      Further, a lower riding attachment has been related to a decreased incidence of lateral meniscus tears.
      • Kim J.E.
      • Choi S.H.
      Is the location of the Wrisberg ligament related to frequent complete discoid lateral meniscus tear?.

       Anatomic Variants of Meniscofemoral Ligaments

      The following anatomical variants are summarized in Table 4.
      Table 4Summary of Previously Described Anatomical Variants
      StudyAnatomical Variant
      Ahn et al.
      • Ahn J.H.
      • Wang J.H.
      • Kim D.U.
      • Lee D.K.
      • Kim J.H.
      Does high location and thickness of the Wrisberg ligament affect discoid lateral meniscus tear type based on peripheral detachment?.
      Discoid lateral meniscus and pMFL
      Anderson et al.
      • Anderson A.F.
      • Awh M.H.
      • Anderson C.N.
      The anterior meniscofemoral ligament of the medial meniscus: Case series.
      Anterior MFL of the medial meniscus, found in 0.44% of 2,745 patients
      Verhey et al.

      Verhey JT, Deckey DG, Tummala S, et al. A novel meniscofemoral ligament variant intra-substance to the PCL [published online November 3, 2021]. Knee Surg Sports Traumatol Arthrosc. https://doi.org/10.1007/s00167-021-06791-6.

      Description of an intra-substance MFL of the PCL; “internal MFL (iMFL)”
      Hamada et al.
      • Hamada M.
      • Miyama T.
      • Nagayama Y.
      • Shino K.
      Repair of a torn medial meniscus with an anteromedial meniscofemoral ligament in an anterior cruciate ligament-injured knee.
      Anteromedial meniscofemoral ligament (amMFL) in an ACL-injured knee
      Kim et al.
      • Kim Y.M.
      • Joo Y.B.
      Anteromedial meniscofemoral ligament of the anterior horn of the medial meniscus: clinical, magnetic resonance imaging, and arthroscopic features.
      Description of amMFL
      Kim et al.
      • Kim Y.-M.
      • Joo Y.-B.
      • Yeon K.-W.
      • Lee K.-Y.
      Anterolateral meniscofemoral ligament of the lateral meniscus.
      Anterolateral MFL of the lateral meniscus (alMFL)
      Rosenberg et al.
      • Rosenberg T.D.
      • Paulos L.E.
      • Parker R.D.
      • Harner C.D.
      • Gurley W.D.
      Discoid lateral meniscus: Case report of arthroscopic attachment of a symptomatic Wrisberg-ligament type.
      Discoid lateral meniscus and pMFL
      Silva and Sampaio
      • Silva A.
      • Sampaio R.
      Anterior lateral meniscofemoral ligament with congenital absence of the ACL.
      alMFL mimicking course of native ACL
      Soejima et al.
      • Soejima T.
      • Murakami H.
      • Tanaka N.
      • Nagata K.
      Anteromedial meniscofemoral ligament.
      Three amMFL cases with variable attachments to lateral meniscus and tibia
      Sonin and Resiter
      • Sonin A.
      • Reister J.A.
      Intra-articular ganglion arising from the meniscofemoral ligament of Humphrey.
      Intra-articular ganglion of the knee arising from aMFL
      ACL, anterior cruciate ligament; alMFL, anterolateral meniscofemoral ligament; amMFL, anteromedial meniscofemoral ligament; aPFL, posterior meniscofemoral ligament; pMFL, posterior meniscofemoral ligament.

       Anteromedial Meniscofemoral Ligament (amMFL)

      A number of studies reviewed reported the presence of the amMFL as a rare structure arising from the root ligament of the anterior horn of the medial meniscus, running anterior to the anterior cruciate ligament and attaching to the posterolateral wall of the femoral intercondylar fossa.
      • Kim Y.M.
      • Joo Y.B.
      Anteromedial meniscofemoral ligament of the anterior horn of the medial meniscus: clinical, magnetic resonance imaging, and arthroscopic features.
      ,
      • Kim Y.-M.
      • Joo Y.-B.
      • Yeon K.-W.
      • Lee K.-Y.
      Anterolateral meniscofemoral ligament of the lateral meniscus.
      ,
      • Soejima T.
      • Murakami H.
      • Tanaka N.
      • Nagata K.
      Anteromedial meniscofemoral ligament.
      ,
      • Trinh J.M.
      • De Verbizier J.
      • Lecocq Texeira S.
      • et al.
      Imaging appearance and prevalence of the anteromedial meniscofemoral ligament: A potential pitfall to anterior cruciate ligament analysis on MRI.
      Kim et al. have suggested there may be a relation of the amMFL to medial meniscus injury secondary to abnormal motion and a larger absolute size as compared with knees without an amMFL.
      • Kim Y.M.
      • Joo Y.B.
      Anteromedial meniscofemoral ligament of the anterior horn of the medial meniscus: clinical, magnetic resonance imaging, and arthroscopic features.
      ,
      • Kim Y.-M.
      • Joo Y.-B.
      • Yeon K.-W.
      • Lee K.-Y.
      Anterolateral meniscofemoral ligament of the lateral meniscus.
      ,
      • Soejima T.
      • Murakami H.
      • Tanaka N.
      • Nagata K.
      Anteromedial meniscofemoral ligament.
      This is particularly true in patients where the amMFL variant does not attach to the tibia and the amMFL acts as an anchor for the anterior horn of the medial meniscus.
      • Hamada M.
      • Miyama T.
      • Nagayama Y.
      • Shino K.
      Repair of a torn medial meniscus with an anteromedial meniscofemoral ligament in an anterior cruciate ligament-injured knee.
      ,
      • Kim Y.M.
      • Joo Y.B.
      Anteromedial meniscofemoral ligament of the anterior horn of the medial meniscus: clinical, magnetic resonance imaging, and arthroscopic features.
      ,
      • Soejima T.
      • Murakami H.
      • Tanaka N.
      • Nagata K.
      Anteromedial meniscofemoral ligament.

       Anterolateral Meniscofemoral Ligament

      The anterolateral meniscofemoral ligament has been described by Kim et al. and Silva et al. as an extremely rare anomaly of the anterior horn of the lateral meniscus which merged with an anteromedial meniscofemoral ligament in some cases and may be associated with agenesis of the anterior cruciate ligament.
      • Kim Y.M.
      • Joo Y.B.
      Anteromedial meniscofemoral ligament of the anterior horn of the medial meniscus: clinical, magnetic resonance imaging, and arthroscopic features.
      ,
      • Kim Y.-M.
      • Joo Y.-B.
      • Yeon K.-W.
      • Lee K.-Y.
      Anterolateral meniscofemoral ligament of the lateral meniscus.
      ,
      • Silva A.
      • Sampaio R.
      Anterior lateral meniscofemoral ligament with congenital absence of the ACL.

      Discussion

      We report, when including MRI, cadaveric, and arthroscopic studies, that the presence of either the anterior or posterior MFL (aMFL, pMFL) to be 70.8%, although this can be highly variable. The presence of both ligaments occurred in approximately 17.6% of individuals. The mean length in both men and women varies, but on average, the aMFL has been reported between 21.6 and 28.3 mm and the pMFL length between 23.4 and 31.2 mm. These ligaments contribute to the complex biomechanics of the knee to synergistically provide stability. In particular, the meniscofemoral ligaments may play a role in allowing the lateral meniscus to augment femorotibial congruency and reduce meniscal contact pressure in both flexion and extension.
      • Forkel P.
      • Herbort M.
      • Sprenker F.
      • Metzlaff S.
      • Raschke M.
      • Petersen W.
      The biomechanical effect of a lateral meniscus posterior root tear with and without damage to the meniscofemoral ligament: Efficacy of different repair techniques.
      Thus, it is the authors’ goal that this review will continue to advance the understanding of the MFLs, their function, and their importance in clinical management.
      Multiple mechanisms have been proposed regarding the precise function of the MFLs during flexion and extension, including a taut pMFL in both flexion and extension versus a reciprocal tightening and loosening of the aMFL and pMFL, both of which result in tangential traction applied to the posterior horn.
      • Last R.J.
      Some anatomical details of the knee joint.
      • Friederich N.F.
      • O’Brien W.R.
      Anterior cruciate ligament graft tensioning versus knee stability.
      • Grood E.S.
      • Hefzy M.S.
      • Lindenfield T.N.
      Factors affecting the region of most isometric femoral attachments. Part I: The posterior cruciate ligament.
      In this review, studies by Gupte et al.
      • Gupte C.M.
      • Smith A.
      • McDermott I.D.
      • Bull A.M.J.
      • Thomas R.D.
      • Amis A.A.
      Meniscofemoral ligaments revisited.
      and Poyton et al.
      • Poynton A.
      • Moran C.J.
      • Moran R.
      • O'Brien M.
      The meniscofemoral ligaments influence lateral meniscal motion at the human knee joint.
      noted an interplay between these ligaments and the lateral meniscus which could play a role in meniscal pathology. It should also be noted that transection of the MFLs has previously shown an increase in femorotibial contact pressure.
      • Forkel P.
      • Herbort M.
      • Sprenker F.
      • Metzlaff S.
      • Raschke M.
      • Petersen W.
      The biomechanical effect of a lateral meniscus posterior root tear with and without damage to the meniscofemoral ligament: Efficacy of different repair techniques.
      However, as noted in this review, MFLs have previously been incorrectly been diagnosed as tears of the lateral meniscus and should be kept in mind when addressing this pathology.
      The medial meniscus has long been thought of as largely fixed, responding only to the direct force applied by the medial femoral condyle and to the modest pull of the deep medial ligament.
      • Bhatia S.
      • Laprade C.M.
      • Ellman M.B.
      • Laprade R.F.
      Meniscal root tears: Significance, diagnosis, and treatment.
      In this review, Kim et al. noted that the presence of an amMFL may be related to medial meniscal injury secondary to abnormal motion. This ligament may anchor to the anterior horn of the medial meniscus altering its motion in flexion and extension.
      In addition to possible protection of the lateral meniscus, the MFLs also support the posterior cruciate ligament in limiting anteroposterior laxity, both as a mechanical and proprioceptive restraint.
      • Gupte C.M.
      • Shaerf D.A.
      • Sandison A.
      • Bull A.M.J.
      • Amis A.A.
      Neural structures within human meniscofemoral ligaments: A cadaveric study.
      As a mechanical restraint, the MFLs provide similar loading capabilities to the posterior fiber bundle of the PCL.
      • Arthur J.R.
      • Haglin J.M.
      • Makovicka J.L.
      • Chhabra A.
      Anatomy and biomechanics of the posterior cruciate ligament and their surgical implications.
      ,
      • Heller L.
      • Langman J.
      The menisco-femoral ligaments of the human knee.
      ,
      • Race A.
      • Amis A.A.
      The mechanical properties of the two bundles of the human posterior cruciate ligament.
      Consequently, an isolated injury to the PCL with preservation of the MFLs may be associated with a reduced posterior draw relative to a combined injury of the PCL and MFLs.
      • LaPrade C.M.
      • Civitarese D.M.
      • Rasmussen M.T.
      • LaPrade R.F.
      Emerging updates on the posterior cruciate ligament: A review of the current literature.
      As a proprioceptive restraint, neural structures contained within the MFLs near their meniscal attachments found in both human cadaveric and animal studies suggest that the MFLs participate in a feedback loop with muscles around the knee to limit posterior draw.
      • Gupte C.M.
      • Shaerf D.A.
      • Sandison A.
      • Bull A.M.J.
      • Amis A.A.
      Neural structures within human meniscofemoral ligaments: A cadaveric study.
      In the context of injury to the PCL and lateral meniscal root, specific evaluation of the MFLs by arthroscopy or MRI may be supported as an indicator of residual function, as intact MFLs may warrant more conservative management of PCL injury. Despite the aforementioned findings, further studies are necessary to elucidate differences in patient outcomes between intact and injured MFLs in a PCL-deficient knee.
      The integral connection between the MFLs, the lateral meniscus, and the PCL has several implications for surgical management. In the case of lateral meniscus tear with disruption of the MFLs, the resulting increase in femorotibial contact pressure necessitates a root repair. As described by Forkel et al., posterior horn fixation reduces lateral compartment pressure to normal values prior to MFL transection.
      • Forkel P.
      • Herbort M.
      • Sprenker F.
      • Metzlaff S.
      • Raschke M.
      • Petersen W.
      The biomechanical effect of a lateral meniscus posterior root tear with and without damage to the meniscofemoral ligament: Efficacy of different repair techniques.
      In associated ACL and posterior root tears, the authors describe a “pullout repair” of the meniscal root through the tibial ACL tunnel, which also normalizes lateral compartment intra-articular pressures.
      • Forkel P.
      • Herbort M.
      • Sprenker F.
      • Metzlaff S.
      • Raschke M.
      • Petersen W.
      The biomechanical effect of a lateral meniscus posterior root tear with and without damage to the meniscofemoral ligament: Efficacy of different repair techniques.
      Additional studies based on finite element analyses further support these findings, as fixation of posterior root during ACL reconstruction in the MFL-deficient knee is postulated to prevent meniscal subluxation and premature osteoarthritis secondary to elevated intra-articular pressures.
      • Knapik D.M.
      • Salata M.J.
      • Voos J.E.
      • Greis P.E.
      • Karns M.R.
      Role of the meniscofemoral ligaments in the stability of the posterior lateral meniscus root after injury in the ACL-deficient knee.
      For partial or total meniscectomy in which removal of the posterior horn is indicated, care must be taken to first transect the MFLs to avoid iatrogenic injury to the posterior knee compartment. The MFL could potentially disrupt the PCL complex upon removal of the posterior horn.
      • Gupte C.M.
      • Smith A.
      • Jamieson N.
      • Bull A.M.J.
      • Thomas R.D.W.
      • Amis A.A.
      Meniscofemoral ligaments—Structural and material properties.
      MRI study with evaluation of MFLs before surgery and specific arthroscopic assessment of MFL status intraoperatively may reduce the risk of PCL damage.
      In instances in which meniscal preservation is no longer an option, the MFLs might also be considered in meniscal allograft transplantation. In meniscal transplantation, current techniques involve total meniscectomy (including release of the MFLs) and attachment of a cryopreserved meniscal allograft to the tibia by open or minimally invasive arthroscopy.
      • Rodkey W.G.
      • Steadman J.R.
      • Li S.T.
      A clinical study of collagen meniscus implants to restore the injured meniscus.
      Many studies demonstrate high rates of complications for meniscal transplant, including tears requiring repair and allograft removal.
      • Rue J.P.H.
      • Yanke A.B.
      • Busam M.L.
      • McNickle A.G.
      • Cole B.J.
      Prospective evaluation of concurrent meniscus transplantation and articular cartilage repair: Minimum 2-year follow-up.
      • McCormick F.
      • Harris J.D.
      • Abrams G.D.
      • et al.
      Survival and reoperation rates after meniscal allograft transplantation: Analysis of failures for 172 consecutive transplants at a minimum 2-year follow-up.
      • Kazi H.A.
      • Abdel-Rahman W.
      • Brady P.A.
      • Cameron J.C.
      Meniscal allograft with or without osteotomy: A 15-year follow-up study.
      • Verdonk P.
      • Beaufils P.
      • Bellemans J.
      • et al.
      Successful treatment of painful irreparable partial meniscal defects with a polyurethane scaffold: Two-year safety and clinical outcomes.
      • Hirschmann M.T.
      • Keller L.
      • Hirschmann A.
      • et al.
      One-year clinical and MR imaging outcome after partial meniscal replacement in stabilized knees using a collagen meniscus implant.
      Preservation of MFLs these procedures may help to maintain normal biomechanical function and reduce complication rates.
      Future studies making use of computer-based motion analysis would be useful in confirming the proposed biomechanical function of MFLs. These studies might also reveal other functions of the MFLs that have not previously been described. Finally, the extent to which MFLs should be considered in management of meniscal, PCL, and combined knee injuries is yet to be determined. Examining outcomes of PCL-deficient knees with intact versus injured MFLs and their response to surgical and nonsurgical treatment would be beneficial in guiding patient-centered treatment.

       Limitations

      The findings of this study should be interpreted in the context of the following limitations. First, many retrospective reviews were included in this study, which are limited by the quality of the data, completeness, and accuracy of reporting. Second, many cadaveric studies are limited by small numbers. Third, the wide range in incidence of MFLs seen could be due to varying modalities of identification, from radiographic to arthroscopic. In addition, owing to the large number of studies reported, study quality was not formally assessed. However, this is a systematic review, which is strengthened by the comprehensiveness of the review, and is a summary of our current, possibly incomplete, understanding of the MFL.

      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 meniscofemoral ligaments in supporting knee stability. Specifically, the MFLs serve an important role in protecting the lateral meniscus and augmenting the function of the PCL.

      Supplementary Data

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