Posterior Cruciate Meniscofemoral Complex Morphology – Functional and Clinical Implications

Sunita Arvind Athavale; Sheetal Kotgirwar; Rekha Lalwani

doi:10.4103/NJCA.NJCA_63_20

ORIGINAL ARTICLE

Year : 2020 | Volume : 9 | Issue : 4 | Page : 159-164

Posterior Cruciate Meniscofemoral Complex Morphology – Functional and Clinical Implications

Sunita Arvind Athavale¹, Sheetal Kotgirwar², Rekha Lalwani²
¹ Additional Professor, Department of Anatomy, All India Institute of Medical Sciences, Bhopal, Madhya Pradesh, India
² Associate Professor, Department of Anatomy, All India Institute of Medical Sciences, Bhopal, Madhya Pradesh, India

Date of Submission	10-Aug-2020
Date of Decision	25-Oct-2020
Date of Acceptance	21-Nov-2020
Date of Web Publication	7-Dec-2020

Correspondence Address:
Rekha Lalwani
Department of Anatomy, All India Institute of Medical Sciences, Bhopal, Madhya Pradesh
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/NJCA.NJCA_63_20

Abstract

Background: The posterior cruciate meniscofemoral ligament (MFL) complex is considered an important stabilizing structure in the human knee joint. Its role in preventing tibial translation and preventing lateral meniscus injuries is increasingly being recognized. The knowledge of the anatomy of this complex, however, lags behind as compared to our knowledge and understating of its counterpart, the anterior cruciate ligament. Methods: Sixteen adult cadaveric knee joints (eight left and eight right) were utilized for this study. The posterior cruciate ligament (PCL) complex was resected out and its morphologic and morphometric assessment was done. Results: The PCL was short and stout ligamentous complex, mostly (but not always) clasped by either anterior MFLs, posterior MFL, or both. The tibial footprint was more or less circular, whereas the femoral footprint was oval and mediolaterally flattened. The PCL was constituted of two distinct fiber bundles, namely anterolateral and posteromedial. The MFLs originated from the posterior margin of the lateral meniscus just proximal to the posterior horn. The two MFLs ascend from their origin, bifurcate, and diverge to clasp the PCL. At least one MFL was observed in all specimens. Conclusion: The anatomical relationship of PCL, meniscofemoral, popliteus, and lateral meniscus suggests that they complement each other for a fine interplay and balance to execute terminal extension while simultaneously protecting the lateral meniscus. The findings of the present study contribute toward improving surgical repairs in double-bundle PCL repairs.

Keywords: Knee joint, lateral meniscus, lateral meniscus injuries, meniscofemoral ligament

How to cite this article:
Athavale SA, Kotgirwar S, Lalwani R. Posterior Cruciate Meniscofemoral Complex Morphology – Functional and Clinical Implications. Natl J Clin Anat 2020;9:159-64

How to cite this URL:
Athavale SA, Kotgirwar S, Lalwani R. Posterior Cruciate Meniscofemoral Complex Morphology – Functional and Clinical Implications. Natl J Clin Anat [serial online] 2020 [cited 2021 Jan 16];9:159-64. Available from: http://www.njca.info/text.asp?2020/9/4/159/302570

Introduction

The posterior cruciate ligament (PCL) is one of the four major ligaments of the knee. It is stronger and thicker than the anterior cruciate ligament (ACL).^[1] The PCL is attached to the lateral surface of the medial condyle of the femur. Two bundles, namely anterolateral and posteromedial, have been identified in PCL which are named according to their femoral attachments.^[2] The anterolateral bundle is taut in flexion and the posteromedial bundle is taut in extension.^[3]

Initially described as the third cruciate ligament, the meniscofemoral ligaments (MFLs) clasp the PCL and have been named the anterior MFLs (aMFLs) and posterior MFLs (pMFL). They are an integral part of PCL complex. These ligaments initially considered to be secondary restraints to the posterior tibial translation^[4] are now considered to play a significant role in:

Stabilizing and protecting the posterolateral tibiofemoral component of the knee
Increasing the congruity of the mobile lateral meniscus and the lateral femoral condyle
Assisting the lateral meniscus in reducing the tibiofemoral contact pressure.^[5]

Different studies have reported different prevalences of these ligaments ranging from 71% to 100%.^[6],[7],[8]

At present, our knowledge of the PCL still lags behind the ACL.^[9] It is known that the success of reconstruction surgeries hinges on precise anatomic restoration. However, there is no consensus on the detailed anatomy of the PCL and the most appropriate method of PCL reconstruction. Improvements in the treatment and the rehabilitation of PCL injuries are based on continued advances in the basic sciences of the PCL.^[10]

Studies have been conducted in various ethnic groups on the PCL complex, but such a study is still wanting in central India.^{[3],[5],[6],[7],[8],[9],[10]}

The present study is undertaken for the detailed observation of the different bundles of the PCL, their footprints, and their associated ligaments for the better comprehension of the anatomy of PCL complex in central Indians to facilitate the design of the PCL reconstruction.

Materials and Methods

This cross-sectional descriptive study was conducted from December 2016 to February 2018 after obtaining ethical clearance from the Institutional Human Ethics Committee of AIIMS, Bhopal. Sixteen adult apparently normal knee joints (8 left and 8 right) obtained from embalmed cadavers of the central India population were utilized for this study. All the limbs were fixed with knee joints in extended positions. The sex of the knee joints utilized could not be ascertained, as already disarticulated lower limbs available in the collection of the department of anatomy were utilized for the study.

Knee joints with any evidence of congenital or acquired knee pathology including osteoarthritis, trauma, or knee joints with evidence of surgical interventions affecting PCL complex were excluded from this study.

The knee joint was exposed from the posterior aspect; the skin over the popliteal fossa was reflected by giving a cruciate incision. The structures and boundaries of the popliteal fossa were cleaned off; also, the connective tissue and the fat were cleared off. The medial and lateral head of gastrocnemius was cut from the origin and reflected. The neuromuscular bundle in the popliteal fossa was cut and reflected. After exposing the fibrous capsule from the posterior aspect, the capsule was cut, giving a medial parasagittal incision and a horizontal incision. This was intended to preserve the PCL complex which is adhered to the fibrous capsule. The fibrous capsule was carefully reflected, separating it from the PCL complex. The MFLs were identified.

The PCL complex was resected by cutting the tibial and femoral attachments, along with the lateral menisci, to preserve the attachments of MFLs on the lateral meniscus.^[11]

To document the footprints of the posterior cruciate ligament

The PCL was detached from its tibial and femoral attachments. The tibial and femoral footprint margins were circumscribed by a permanent marker. These footprints were then translated on a piece of glass plate by apposing each footprint onto the glass plate and creating a replica of the footprint on the surface of the glass plate. These were then further translated and charted on a graph paper to calculate the surface area of each footprint [Figure 1].

Figure 1: Surface area charting of posterior cruciate ligament

Click here to view

The length of PCL was measured from the most anterior point of tibial footprint to the most anterior point of femoral footprint with the help of thread and vernier caliper.^[12],[13]

The synovial membrane was carefully removed. The MFLs and different fiber bundles along with their relative positions were identified under a magnifying glass. Disposition of fibers in individual fiber bundles was also noted.

Statistical analysis of the morphometric measurements for descriptive statistics was done on SPSS software.

Results

The PCL was short and stout ligamentous complex, mostly (but not always) clasped by either aMFL, pMFL, or both [Figure 2]a and [Figure 2]b. Tibial footprint was more or less circular, whereas the femoral footprint was oval and mediolaterally flattened. The PCL was constituted of two distinct fiber bundles, namely anterolateral and posteromedial with respect to their attachment on the tibia. The anterolateral was cord like and posteromedial bundle fanned out superolaterally [Figure 3]a and [Figure 3]b.

Figure 2: (a) Posterior cruciate ligament complex of left along with lateral meniscus, anterior cruciate ligament and popliteus muscle, (b) Showing schematic diagram of posterior cruciate ligament complex-related structure: aMFL: Anterior meniscofemoral ligament, pMFL: Posterior meniscofemoral ligament

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Figure 3: (a) Two distinct bundles of posterior cruciate ligament of the left knee. (b) Show schematic diagram of the posterior cruciate ligament of the left knee: AL: Anterolateral bundle, PM: Posteromedial bundl

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The length of PCL was 30.7 ± 5.3 mm on the right side and 29 ± 7.6 mm on the left side. The difference between the two sides was statistically not significant. [Table 1] shows descriptive statistics of the morphometric assessment of PCL and its components. The difference between the two sides was statistically not significant. The tibial and femoral footprints were positively and significantly correlated with each other (Pearson’s correlation 0.576 and P < 0.05). The two bundles, anterolateral and posteromedial, were almost similar in length [Table 1] and showed slight negative correlation as regards to their length. However this was statistically not significant.

Table 1: Descriptive statistics of various parameters of posterior cruciate ligament

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Meniscofemoral ligament

The MFLs originated from the posterior margin of lateral meniscus just proximal to the posterior horn. The two MFLs ascend from their origin, bifurcate, and diverge to clasp the PCL [Figure 4]a.

Figure 4: (a) Anterior meniscofemoral ligament and posterior meniscofemoral ligament clasping the posterior cruciate ligament, (b) showing extension of posterior horn of lateral meniscus extending further medially

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The fibers of MFLs were aligned obliquely with respect to PCL. The fiber arrangement of aMFL and pMFL also varied with respect to each other, as they do not run parallel to each other. The origin of pMFL was very close and sometimes confluent with the origin of the popliteus muscle. Both meniscofemorals were attached to the femur at the other attachment. The aMFL was relatively more horizontal than pMFL [Figure 2]a.

[Table 2] shows the number and percentage of prevalence of MFLs in the present study.

Table 2: Number and percentage of prevalence of meniscofemoral ligament in the present study

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The posterior end of the lateral meniscus sometimes extended further medially giving a “J” shape to the meniscus [Figure 4]b.

Few notable observations were as follows. In three cases, the pMFL was appreciably larger [Figure 5]a and [Figure 5]b and in one case, aMFL was appreciably prominent.

Figure 5: (a and b) Larger posterior meniscofemoral ligament of the right and left sides: PCL: posterior cruciate ligament

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Discussion

Posterior cruciate ligament morphology

Primarily designed to resist the posterior translation of the tibia on the femur in all positions of the knee joint, the two bundles are meant to resist this translation in different positions.^[14],[15] The present study also observed similar bundles. However, in contrast to the observations by Kweon et al.^[14] and LaPadre et al.,^[16] the anterolateral was cord like rather than the posteromedial bundle.

The PCL length as observed in the present study is lower than that of previous studies by about 8 mm.^[14],[15] This may be due to racial differences (previous studies have been conducted on the Caucasian population) or due to different landmarks used for measuring length.

Our findings of difference in cross-sectional area of tibial and femoral footprints (tibial being more than twice than femoral) corroborate with findings of studies reported by LaPrade et al.^[16]

Meniscofemoral ligament

Various cadaveric and radiological studies have reported variable prevalences of MFL. The presence of at least one MFL was documented in the range of 71–100%, bilateral presence was documented in 5–50% of cases. The prevalence of pMFL was higher than aMFL, especially in radiological studies,^{[17],[18],[19],[20],[21]} as recognition of aMFL is difficult in magnetic resonance imaging owing to its smaller size.

aMFL is generally believed to be thinner than that of pMFL. However, the present study documented one case of appreciably thick aMFL. Investigators have reported that two bundles of PCL have a significant primary role in resisting posterior tibial translation throughout the range of flexion of the knee joint.^{[15],[16],[17],[18],[19],[20],[21],[22]}

MFLs are also considered as secondary restrain for posterior tibial translation. A study by Gupte et al.^[20] has documented MFLs contribute to 28% resistance to posterior tibial translation in the intact knee and 70% in PCL-deficient knee, thereby lending evidence to the hypothesis that MFLs are secondary restraints to the posterior tibial translations.

The role of MFL in mobility of the posterior horn of the lateral meniscus has not been discussed much. The authors tend to agree with the proposition of Last^[23] and Simonian et al.^[24] that the fine control of exerted by MFLs and popliteus in antagonist fashion [Figure 2]a and [Figure 2]b prevents tears of the lateral meniscus.

The posterior tibial attachment of lateral meniscus is a peculiarly human feature after assumption of erect posture. Its purpose is to restrict anteroposterior movements of the lateral meniscus to reinforce the knee extension stability.^[25],[26] The MFL along with the popliteus muscle has a significant role to play in fine-tuning the lateral meniscus movement.

There is an ongoing debate and recent literature is favoring the superiority of double-bundle repair.^[27] The findings of the present study hence may be utilized, especially for the Indian population, as the studies till date are lacking in Indian data.

Conclusion

PCL complex consisted of PCL and two MFLs clasping it. PCL is constituted of two distinct fiber bundles, namely anterolateral and posteromedial. At least one MFLs is present in all specimens studied. The tibial and femoral footprints differ in morphology and morphometry.

The anatomical relationship of PCL, meniscofemoral, popliteus, and lateral meniscus suggests that they complement each other for affine interplay and balance to execute terminal extension while simultaneously protecting the lateral meniscus. The findings of the present study will contribute toward improving surgical repairs in double-bundle PCL repairs.

Limitation of the study

The present study is conducted on a small population; a study on a larger population is desirable for aiding PCL reconstruction. As the sex of the anatomical specimen was not known, hence the gender-specific measurements could not be taken.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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