Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14 DOI 10.1007/s00167-014-3476-5
KNEE
Medial meniscus anatomy—from basic science to treatment Robert S´migielski · Roland Becker · Urszula Zdanowicz · Bogdan Ciszek
Received: 5 December 2014 / Accepted: 6 December 2014 / Published online: 24 December 2014 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2014
Abstract This paper focuses on the anatomical attachment of the medial meniscus. Detailed anatomical dissections have been performed and illustrated. Five zones can be distinguished in regard to the meniscus attachments anatomy: zone 1 (of the anterior root), zone 2 (anteromedial zone), zone 3 (the medial zone), zone 4 (the posterior zone) and the zone 5 (of the posterior root). The understanding of the meniscal anatomy is especially crucial for meniscus repair but also for correct fixation of the anterior and posterior horn of the medial meniscus.
understand its importance and also improve the anatomical approach to its repair. There are many anatomical studies about menisci. The current paper focuses on the anatomy of the medial meniscus. This anatomical study was performed with the specific intention of identifying the meniscus insertions, which is of relevance to meniscus surgery.
Keywords Anatomy · Medial meniscus · Attachment
The medial meniscus forms almost a semicircular shape and covers up to 50–60 % of the articular surface of medial tibial plateau [4] (Fig. 1a, b). The width of the medial meniscus is about 11 mm significantly bigger at the posterior region and becomes gradually smaller towards the anterior horn. During knee flexion, the main loading occurs at the posterior region of the meniscus [2]. The posterior horn of the meniscus slides slightly over the posterior rim of the tibial plateau during deep knee flexion. This is the moment where significant stress occurs on the posterior horn and should be avoided early on after meniscus repair. Five anatomical zones of the medial meniscus are distinguishable in regard to the meniscus anatomy: the anterior root (zone 1); the anteromedial zone (zone 2a and 2b); the medial zone (zone 3); the posterior zone (zone 4); and the posterior root (zone 5) (Fig. 2). This zonal division is based on different anatomical characteristics and is in contrast to the previous descriptions. Weiss et al. [17] divided the medial meniscus into five equal parts, each one representing exactly one-fifth of the length [17]. This was modified by Yagishita et al. [19] by combining the anterior and anterior junctional zone into one, resulting in four zones.
Introduction The menisci have received increased attention during the last two decades. Numerous clinical studies have proven the importance of the menisci for joint protection and prevention of early osteoarthritis [5, 15]. A better understanding of meniscus anatomy may help surgeons to
R. S´migielski (*) · U. Zdanowicz Orthopaedic and Sports Traumatology Department, Carolina Medical Center, Pory 78, 02‑757 Warsaw, Poland e-mail: [email protected]; [email protected] URL: http://www.carolina.pl R. Becker Department of Orthopaedic and Traumatology, City Hospital Brandenburg, Brandenburg, Germany B. Ciszek Department of Descriptive and Clinical Anatomy, Medical University of Warsaw, Warsaw, Poland
13
Gross anatomy
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14
Fig. 1 a Anatomical dissection of proximal tibial articular surface (plan view, femur removed). 1 medial meniscus; 2 lateral meniscus; 3 tibial attachment of anterior cruciate ligament; and 4 tibial attachment of posterior cruciate ligament. b The medial meniscus covers up to 50–60 % of the articular surface of medial tibial condyle. ACL ante-
9
rior cruciate ligament, PCL posterior cruciate ligament, MTC medial tibial condyle, LTC lateral tibial condyle, aMM anterior root of medial meniscus, pMM posterior root of medial meniscus, aML anterior root of lateral meniscus, pML posterior root of lateral meniscus
Fig. 3 Zone 1 of medial meniscus. Anatomical dissection showing type 1 of anterior tibial attachment of medial meniscus (marked with black arrows). ACL anterior cruciate ligament, aMM anterior root of medial meniscus, aML anterior root of lateral meniscus
Fig. 2 Anatomical dissection showing five anatomical zones within medial meniscus. ACL anterior cruciate ligament, tl transverse ligament (anterior intermeniscal ligament), PT patellar tendon, PCL posterior cruciate ligament, ML lateral meniscus, PoT Popliteus tendon, hl Humphry ligament (anterior menisco-femoral ligament)
Zone 1—anterior root As Homo sapiens changed from occasional to habitual bipedalism, the anatomy of the human menisci also changed. In contrast to tetrapods, there are two tibial insertions indicating the full extension phase during gate [16]. The anterior root of the medial meniscus is located proximal to the superior aspect of the medial edge of the medial
tibial tuberosity and proximal and medial to the centre of the superior edge of the tibial tuberosity [9]. According to Berlet et al. [1], there are four insertion patterns of the anterior root of the medial meniscus. Type I, the most frequent (Fig. 3), has the insertion located in the flat intercondylar region of the tibial plateau (also called by Jacobsen the cristae area intercondylaris anterior). Type II has a more medial insertion, closer to articular tibial surface. Type III has a more anterior insertion, which is on the downslope of tibia. Type IV shows no solid fixation, and only coronal fibres control meniscus stability. The insertion site of the anterior root includes supplementary, lower density fibres. The mean total tibial attachment area is about 110.4 mm2, but only 50 % belong to the
13
10
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14
central, prominent root fibres (mean 56.3 mm2), which are the most dense [9]. Radiographic landmarks were identified in order to describe the attachment of the anterior horn [7]. The following measurements are used on antero-posterior radiographs: • 2.8 mm distal to proximal joint line • 3.1 mm medial to medial tibial eminence line • 17 mm medial to lateral tibial eminence line On the lateral radiographic view, the following measurements were identified: • 12.2 mm anterior to tibial long axis • 19.3 mm proximal to champagne glass drop (CGD) line • 4.8 mm posterior to anterior tibial plateau line [8] Rainio et al. [12] describe atypical insertion sites of anterior root to anterior cruciate ligament in 1 % of cases. The absence or the hypermobility of the anterior root of the medial meniscus is one of the major anomalies. However in all cases, the oblique ligament was present connecting the anterior horn of medial meniscus to the proximal area of anterior cruciate ligament.
Fig. 4 Anatomical dissection of anterior aspect of the left knee joint. Within zone 2a superior edge of medial meniscus remains free and has no connections to surrounding tissues (marked with arrows). MM medial meniscus, ML lateral meniscus, MFC medial femoral condyle, LFC lateral femoral condyle, ACL anterior cruciate ligament, PCL posterior cruciate ligament, HP Hoffa pad
Zone 2—anteromedial zone The anteromedial zone includes the anterior horn of medial meniscus and finishes with the anterior border of the medial collateral ligament. The zone can be further divided into two sub-zones: anterior 2a (from anterior root to the transverse ligament) and 2b (from transverse ligament to anterior border of the medial collateral ligament (Fig. 2). The meniscus of zone 2a, 2b, 3, 4 attaches to the tibia by inferior periphery only, with menisco-tibial ligament (also called coronary ligament) [9, 10]. Although described in previous studies [13, the outer border of the medial meniscus in zone 2 is not attached to the joint capsule. The superior periphery of medial meniscus at zone 2a shows no attachment to the surrounding tissues (Fig. 4). In zone 2b, however, the most superior periphery of the meniscus is attached to the synovial tissue (Fig. 5).
Zone 3—region of the medial collateral ligament This is the only zone where the entire periphery of the meniscus is attached to the joint capsule. The lower part is attached via the coronary ligament (menisco-tibial ligament) and the upper part with the menisco-femoral ligament (Fig. 6). Cross sections of medial meniscus in zone 3 showed the attachment to the joint capsule (Fig. 7a, b).
13
Fig. 5 Anatomical dissection of antero-medial aspect of the knee joint. Within zone 2b outer and superior border of medial meniscus is connected to synovial tissue (marked with arrows). MM medial meniscus, MFC medial femoral condyle, ACL anterior cruciate ligament
In contrast to previous studies, which have reported a firm attachment to the deep layer of the medial collateral ligament [18], we could not confirmed that in current study. Anatomical dissection as well as histology of specimens
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14
11
However, the so-called deep layer of the medial collateral ligament might be a kind of reinforcement of the joint capsule, analogous to what is described in the shoulder.
Zone 4—posterior horn The superior part of the meniscus periphery in zone 4 does not attach to the capsule (Fig. 8a, d). The inferior part, in contrast, attaches to the tibia via loose connective tissue, forming the menisco-tibial (coronary) ligament. The menisco-tibial ligament attaches to the tibia about 7–10 mm below the level of articular cartilage and forms a posterior femoral recess in this zone [6] (Figs. 9, 10). There is a wide area of the superior periphery of the posterior horn, which shows no attachment to the capsule.
Fig. 6 Anatomical dissection at the level of zone 3 of medial meniscus (at the level of medial collateral ligament, MCL). At this point, meniscus attaches fully to joint capsule (marked with white arrows). MM medial meniscus, MTC medial tibial condyle
Zone 5—posterior root
showed only one layer of medial collateral ligament. The meniscus was attached to the joint capsule, separated from medial collateral ligament with loose connective tissue.
The insertion site of the posterior root is located (Figs. 11, 12) 9.6 mm posterior and 0.7 mm lateral from medial apex of the tibial eminence, 3.5 mm lateral to the articular cartilage inflection point of the medial tibial plateau and 8.2 mm anterior to the most superior tibial attachment of posterior cruciate ligament [8].
Fig. 7 Histology (light microscopy, H&E stain, original magnification ×4) of cross section of medial meniscus, at the level of medial collateral ligament (zone 3): macroscopic view (a) and microscopic
view (b). MCL medial collateral ligament, MM medial meniscus, JC joint capsule, 1 loos connective tissue separating medial collateral ligament from joint capsule, 2 blood vessels
13
12
Fig. 8 Anatomical dissection of zone 4 of medial meniscus (a). Menisco-tibial (coronary) ligament is marked with white arrows (b, c). Medial collateral ligament is marked with black arrows (b), notice: the level of attachment of menisco-tibial (coronary) ligament on the tibia. MM medial meniscus, MTC medial tibial condyle. His-
Fig. 9 Anatomical dissection of posterior aspect of the left knee joint. Posterior femoral recess is marked with black arrows. Notice: free superior edge of posterior horn of medial meniscus. LFC lateral femoral condyle, ML lateral meniscus, PT popliteal tendon, PCL posterior cruciate ligament, MM medial meniscus, JC joint capsule, MFC medial femoral condyle, 1 proximal attachment of lateral head of gastrocnemius muscle, 2 distal attachment of ilio-tibial band, 3 distal attachment of biceps tendon, 4 lateral collateral ligament, 5 proximal attachment of medial head of gastrocnemius muscle, 6 distal attachment of semimembranous tendon
The radiographic landmarks of the tibial attachment in the antero-posterior and lateral view are the following [7]. Anteroposterior view • 4.8 mm proximal to the proximal joint line • 2.3 mm lateral to medial tibial eminence line • 12.7 mm medial to lateral tibial eminence line
13
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14
tology (d) (light microscopy, H&E stain, original magnification ×4) of cross section of medial meniscus within zone 4. Menisco-tibial (coronary) ligament is marked with white arrows. Notice: curved shape (marked with yellow arrows) of superior edge of medial meniscus within this zone, with no attachments to surrounding tissues
Fig. 10 Anatomical dissection of left knee joint. Postero-medial femoral recess is marked with yellow arrows. MCL medial collateral ligament, MM medial meniscus, JC joint capsule, PCL posterior cruciate ligament, ACL anterior cruciate ligament, magnification of posteromedial femoral recess
Lateral view • 24.1 mm posterior to tibial long axis • 21.8 mm proximal to CGD line • 18 mm anterior to posterior tibial plateau line [7]
Connections between medial and lateral meniscus There are four different menisco-meniscal ligaments connecting the medial with the lateral meniscus [20]: the medial oblique intermeniscal ligaments; the lateral oblique intermeniscal ligaments; the anterior ligament (also called
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14
13
Fig. 11 Anatomical dissection of proximal tibial articular surface (plan view, femur removed). Tibial attachment of posterior root of medial meniscus is marked with white arrows. PCL posterior cruciate ligament, aMFL anterior menisco-femoral ligament (Humphry ligament), pML posterior root of lateral meniscus, ACL anterior cruciate ligament, aML anterior root of lateral meniscus, aMM anterior root of medial meniscus, pMM posterior root of medial meniscus, TL transverse ligament (anterior menisco-meniscal ligament), MCL medial collateral ligament
transverse ligament); and the posterior intermeniscal ligament. The transverse ligament (anterior intermeniscal or anterior menisco-meniscal ligament) is present in 60–94 % of all knees [1, 11]. In contrast, the posterior intermeniscal ligament can be found in 1–4 % of cases only [3]. The medial oblique intermeniscal ligament, which is present in 1 % of knees, takes its name from its anterior meniscal point of origin, begins from the central part of the anterior root of medial meniscus and passes obliquely backwards to the upper part of the posterior horn of the lateral meniscus. Consequently, lateral intermeniscal ligaments, which are present in 4 % of knees, extend from the anterior root of lateral meniscus, passing between the cruciates and inserting into the upper part of the posterior root of the medial meniscus. Chan et al. [3] also described two cases of unilateral menisco-meniscal ligament: lateral and medial. In those cases, there was additional connection between anterior and posterior horn of each meniscus. Both ligaments were identified on MRI, and a unilateral medial menisco-meniscal ligament was also confirmed by arthroscopy.
Clinical relevance Although meniscal surgery is one of the most frequent procedures in orthopaedics, a more detailed understanding
Fig. 12 Magnification of anatomical dissection of posterior aspect of the knee joint. Posterior root of medial meniscus is marked with white arrows. 1 posterior cruciate ligament, 2 anterior menisco-femoral ligament, 3 posterior root of lateral meniscus, 4 tibial attachment of anterior cruciate ligament, 5 anterior root of lateral meniscus
of the menisci’s anatomy is likely required to improve the success of repairs or replacements. Dividing the medial meniscus into five anatomical zones, as described here, has important implications for meniscal treatment. In each zone, a different suturing technique is required for anatomical reconstruction. Knowing the exact anatomy of zones 1 and 5—anterior and posterior root—is important especially for meniscal transplantation. In order to anatomically suture anterior and/or posterior root of medial meniscus, we need to restore rigid bone fixation through transosseous suturing. Differences of as little as 2–3 mm have a significant impact on the meniscus function [14]. The insertion of the meniscus transplant more medially will cause significant extrusion and an increase in femorotibial loading. On the other hand, the meniscus transplant becomes very vulnerable if the insertion is too close to the tibial eminentia because of overloading. Considering the attachment of the medial meniscus in zone 2a, the inferior vertical suture technique is recommended in order to restore the menisco-tibial ligament. This is slightly different in zone 2b, because of the attachment
13
14
of the inferior and superior part of the meniscus periphery. Zone 3 requires two vertical sutures from the anatomical point of view in order to restore both the menisco-tibial (coronal) and menisco-femoral ligaments. However, it might be a challenge to suture the meniscus to the joint capsule (which some authors [17] also call the deep layer of medial collateral ligament) alone, instead to the medial collateral ligament (superficial layer). The solution would be to use absorbable sutures that allow, in time, independent movement between medial collateral ligament and joint capsule. Zone 4 seems to be the most controversial. Our anatomical study showed only the attachment of the inferior part of the meniscus periphery to tibia. At the same time, this is the most challenging and technically difficult area for meniscus repair. Many surgeons are satisfied suturing this part of the meniscus to the posterior capsule, but it may have a significant impact on the mobility of the posteromedial corner. There is a wide space between outer surface of zone 4 of medial meniscus and the joint capsule. Suturing the meniscus to the joint capsule will close the recess and subsequently impair the mobility of the medial meniscus, which may significantly change the position of meniscus during knee movement. For this reason, a more anatomically suture placement in zone 4 should be considered. Acknowledgments The authors gratefully acknowledge Maciej Pronicki, MD, PhD for providing histopathology examinations, Maciej S´miarowski ([email protected]) for taking all photographs and Center for Medical Education (www.cemed.pl) for its help.
References 1. Berlet GC, Fowler PJ (1998) The anterior horn of the medial meniscus an anatomic study of its insertion. Am J Sports Med Am Orthop Soc Sports Med 26:540–543 2. Becker R, Wirz D, Wolf C, Göpfert B, Nebelung W, Friederich N (2005) Measurement of meniscofemoral contact pressure after repair of bucket-handle tears with biodegradable implants. Arch Orthop Trauma Surg 125(4):254–602 3. Chan CM, Goldblatt JP (2012) Unilateral meniscomeniscal ligament. Orthopedics 35:e1815–e1817 4. Clark CR, Ogden JA (1983) Development of the menisci of the human knee joint. Morphological changes and their potential role in childhood meniscal injury. J Bone Joint Surg Am 65:538–547
13
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14 5. Englund M (2008) The role of the meniscus in osteoarthritis genesis. Rheum Dis Clin North Am 34:573–579 6. Fenn S, Datir A, Saifuddin A (2009) Synovial recesses of the knee: MR imaging review of anatomical and pathological features. Skelet Radiol 38:317–328 7. James EW, LaPrade CM, Ellman MB, Wijdicks CA, Engebretsen L, LaPrade RF (2014) Radiographic identification of the anterior and posterior root attachments of the medial and lateral menisci. Am J Sports Med 42:2707–2714 8. Johannsen AM, Civitarese DM, Padalecki JR, Goldsmith MT, Wijdicks CA, LaPrade RF (2012) Qualitative and quantitative anatomic analysis of the posterior root attachments of the medial and lateral menisci. Am J Sports Med 40:2342–2347 9. LaPrade CM, Ellman MB, Rasmussen MT, James EW, Wijdicks CA, Engebretsen L, LaPrade RF (2014) Anatomy of the anterior root attachments of the medial and lateral menisci: a quantitative analysis. Am J Sports Med 42:2386–2392 10. Lougher L, Southgate CR, Holt MD (2003) Coronary liga ment rupture as a cause of medial knee pain. Arthroscopy 19:e157–e158 11. Masouros SD, McDermott ID, Amis AA, Bull AM (2008) Biomechanics of the meniscus-meniscal ligament construct of the knee. Knee Surg Sports Traumatol Arthrosc 16:1121–1132 12. Rainio P, Sarimo J, Rantanen J, Alanen J, Orava S (2002) Observation of anomalous insertion of the medial meniscus on the anterior cruciate ligament. Arthrosc J Arthrosc Relat Surg 18:1–6 13. Rath E, Richmond JC (2000) The menisci: basic science and advances in treatment. Br J Sports Med 34:252–257 14. Stärke C, Kopf S, Gröbel KH, Becker R (2010) The effect of a nonanatomic repair of the meniscal horn attachment on meniscal tension: a biomechanical study. Arthroscopy 26:358–365 15. Stein T, Mehling AP, Welsch F, von Eisenhart-Rothe R, Jäger A (2010) Long-term outcome after arthroscopic meniscal repair versus arthroscopic partial meniscectomy for traumatic meniscal tears. Am J Sports Med 38:1542–1548 16. Tardieu C, Dupont JY (2001) The origin of femoral trochlear dysplasia: comparative anatomy, evolution, and growth of the patellofemoral joint. Rev Chir Orthop Reparatrice Appar Mot 87:373–383 17. Weiss CB, Lundberg M, Hamberg P, DeHaven KE, Gillquist J (1989) Non-operative treatment of meniscal tears. J Bone Joint Surg Am 71:811–822 18. Wymenga AB, Kats JJ, Kooloos J, Hillen B (2006) Surgical anatomy of the medial collateral ligament and the posteromedial capsule of the knee. Knee Surg Sports Traumatol Arthrosc 14:229–234 19. Yagishita K, Muneta T, Ogiuchi T, Sekiya I, Shinomiya K (2004) Healing potential of meniscal tears without repair in knees with anterior cruciate ligament reconstruction. Am J Sports Med 32:1953–1961 20. Zivanović S (1974) Menisco-meniscal ligaments of the human knee joint. Anat Anz 135:35–42
KNEE
Medial meniscus anatomy—from basic science to treatment Robert S´migielski · Roland Becker · Urszula Zdanowicz · Bogdan Ciszek
Received: 5 December 2014 / Accepted: 6 December 2014 / Published online: 24 December 2014 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2014
Abstract This paper focuses on the anatomical attachment of the medial meniscus. Detailed anatomical dissections have been performed and illustrated. Five zones can be distinguished in regard to the meniscus attachments anatomy: zone 1 (of the anterior root), zone 2 (anteromedial zone), zone 3 (the medial zone), zone 4 (the posterior zone) and the zone 5 (of the posterior root). The understanding of the meniscal anatomy is especially crucial for meniscus repair but also for correct fixation of the anterior and posterior horn of the medial meniscus.
understand its importance and also improve the anatomical approach to its repair. There are many anatomical studies about menisci. The current paper focuses on the anatomy of the medial meniscus. This anatomical study was performed with the specific intention of identifying the meniscus insertions, which is of relevance to meniscus surgery.
Keywords Anatomy · Medial meniscus · Attachment
The medial meniscus forms almost a semicircular shape and covers up to 50–60 % of the articular surface of medial tibial plateau [4] (Fig. 1a, b). The width of the medial meniscus is about 11 mm significantly bigger at the posterior region and becomes gradually smaller towards the anterior horn. During knee flexion, the main loading occurs at the posterior region of the meniscus [2]. The posterior horn of the meniscus slides slightly over the posterior rim of the tibial plateau during deep knee flexion. This is the moment where significant stress occurs on the posterior horn and should be avoided early on after meniscus repair. Five anatomical zones of the medial meniscus are distinguishable in regard to the meniscus anatomy: the anterior root (zone 1); the anteromedial zone (zone 2a and 2b); the medial zone (zone 3); the posterior zone (zone 4); and the posterior root (zone 5) (Fig. 2). This zonal division is based on different anatomical characteristics and is in contrast to the previous descriptions. Weiss et al. [17] divided the medial meniscus into five equal parts, each one representing exactly one-fifth of the length [17]. This was modified by Yagishita et al. [19] by combining the anterior and anterior junctional zone into one, resulting in four zones.
Introduction The menisci have received increased attention during the last two decades. Numerous clinical studies have proven the importance of the menisci for joint protection and prevention of early osteoarthritis [5, 15]. A better understanding of meniscus anatomy may help surgeons to
R. S´migielski (*) · U. Zdanowicz Orthopaedic and Sports Traumatology Department, Carolina Medical Center, Pory 78, 02‑757 Warsaw, Poland e-mail: [email protected]; [email protected] URL: http://www.carolina.pl R. Becker Department of Orthopaedic and Traumatology, City Hospital Brandenburg, Brandenburg, Germany B. Ciszek Department of Descriptive and Clinical Anatomy, Medical University of Warsaw, Warsaw, Poland
13
Gross anatomy
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14
Fig. 1 a Anatomical dissection of proximal tibial articular surface (plan view, femur removed). 1 medial meniscus; 2 lateral meniscus; 3 tibial attachment of anterior cruciate ligament; and 4 tibial attachment of posterior cruciate ligament. b The medial meniscus covers up to 50–60 % of the articular surface of medial tibial condyle. ACL ante-
9
rior cruciate ligament, PCL posterior cruciate ligament, MTC medial tibial condyle, LTC lateral tibial condyle, aMM anterior root of medial meniscus, pMM posterior root of medial meniscus, aML anterior root of lateral meniscus, pML posterior root of lateral meniscus
Fig. 3 Zone 1 of medial meniscus. Anatomical dissection showing type 1 of anterior tibial attachment of medial meniscus (marked with black arrows). ACL anterior cruciate ligament, aMM anterior root of medial meniscus, aML anterior root of lateral meniscus
Fig. 2 Anatomical dissection showing five anatomical zones within medial meniscus. ACL anterior cruciate ligament, tl transverse ligament (anterior intermeniscal ligament), PT patellar tendon, PCL posterior cruciate ligament, ML lateral meniscus, PoT Popliteus tendon, hl Humphry ligament (anterior menisco-femoral ligament)
Zone 1—anterior root As Homo sapiens changed from occasional to habitual bipedalism, the anatomy of the human menisci also changed. In contrast to tetrapods, there are two tibial insertions indicating the full extension phase during gate [16]. The anterior root of the medial meniscus is located proximal to the superior aspect of the medial edge of the medial
tibial tuberosity and proximal and medial to the centre of the superior edge of the tibial tuberosity [9]. According to Berlet et al. [1], there are four insertion patterns of the anterior root of the medial meniscus. Type I, the most frequent (Fig. 3), has the insertion located in the flat intercondylar region of the tibial plateau (also called by Jacobsen the cristae area intercondylaris anterior). Type II has a more medial insertion, closer to articular tibial surface. Type III has a more anterior insertion, which is on the downslope of tibia. Type IV shows no solid fixation, and only coronal fibres control meniscus stability. The insertion site of the anterior root includes supplementary, lower density fibres. The mean total tibial attachment area is about 110.4 mm2, but only 50 % belong to the
13
10
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14
central, prominent root fibres (mean 56.3 mm2), which are the most dense [9]. Radiographic landmarks were identified in order to describe the attachment of the anterior horn [7]. The following measurements are used on antero-posterior radiographs: • 2.8 mm distal to proximal joint line • 3.1 mm medial to medial tibial eminence line • 17 mm medial to lateral tibial eminence line On the lateral radiographic view, the following measurements were identified: • 12.2 mm anterior to tibial long axis • 19.3 mm proximal to champagne glass drop (CGD) line • 4.8 mm posterior to anterior tibial plateau line [8] Rainio et al. [12] describe atypical insertion sites of anterior root to anterior cruciate ligament in 1 % of cases. The absence or the hypermobility of the anterior root of the medial meniscus is one of the major anomalies. However in all cases, the oblique ligament was present connecting the anterior horn of medial meniscus to the proximal area of anterior cruciate ligament.
Fig. 4 Anatomical dissection of anterior aspect of the left knee joint. Within zone 2a superior edge of medial meniscus remains free and has no connections to surrounding tissues (marked with arrows). MM medial meniscus, ML lateral meniscus, MFC medial femoral condyle, LFC lateral femoral condyle, ACL anterior cruciate ligament, PCL posterior cruciate ligament, HP Hoffa pad
Zone 2—anteromedial zone The anteromedial zone includes the anterior horn of medial meniscus and finishes with the anterior border of the medial collateral ligament. The zone can be further divided into two sub-zones: anterior 2a (from anterior root to the transverse ligament) and 2b (from transverse ligament to anterior border of the medial collateral ligament (Fig. 2). The meniscus of zone 2a, 2b, 3, 4 attaches to the tibia by inferior periphery only, with menisco-tibial ligament (also called coronary ligament) [9, 10]. Although described in previous studies [13, the outer border of the medial meniscus in zone 2 is not attached to the joint capsule. The superior periphery of medial meniscus at zone 2a shows no attachment to the surrounding tissues (Fig. 4). In zone 2b, however, the most superior periphery of the meniscus is attached to the synovial tissue (Fig. 5).
Zone 3—region of the medial collateral ligament This is the only zone where the entire periphery of the meniscus is attached to the joint capsule. The lower part is attached via the coronary ligament (menisco-tibial ligament) and the upper part with the menisco-femoral ligament (Fig. 6). Cross sections of medial meniscus in zone 3 showed the attachment to the joint capsule (Fig. 7a, b).
13
Fig. 5 Anatomical dissection of antero-medial aspect of the knee joint. Within zone 2b outer and superior border of medial meniscus is connected to synovial tissue (marked with arrows). MM medial meniscus, MFC medial femoral condyle, ACL anterior cruciate ligament
In contrast to previous studies, which have reported a firm attachment to the deep layer of the medial collateral ligament [18], we could not confirmed that in current study. Anatomical dissection as well as histology of specimens
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14
11
However, the so-called deep layer of the medial collateral ligament might be a kind of reinforcement of the joint capsule, analogous to what is described in the shoulder.
Zone 4—posterior horn The superior part of the meniscus periphery in zone 4 does not attach to the capsule (Fig. 8a, d). The inferior part, in contrast, attaches to the tibia via loose connective tissue, forming the menisco-tibial (coronary) ligament. The menisco-tibial ligament attaches to the tibia about 7–10 mm below the level of articular cartilage and forms a posterior femoral recess in this zone [6] (Figs. 9, 10). There is a wide area of the superior periphery of the posterior horn, which shows no attachment to the capsule.
Fig. 6 Anatomical dissection at the level of zone 3 of medial meniscus (at the level of medial collateral ligament, MCL). At this point, meniscus attaches fully to joint capsule (marked with white arrows). MM medial meniscus, MTC medial tibial condyle
Zone 5—posterior root
showed only one layer of medial collateral ligament. The meniscus was attached to the joint capsule, separated from medial collateral ligament with loose connective tissue.
The insertion site of the posterior root is located (Figs. 11, 12) 9.6 mm posterior and 0.7 mm lateral from medial apex of the tibial eminence, 3.5 mm lateral to the articular cartilage inflection point of the medial tibial plateau and 8.2 mm anterior to the most superior tibial attachment of posterior cruciate ligament [8].
Fig. 7 Histology (light microscopy, H&E stain, original magnification ×4) of cross section of medial meniscus, at the level of medial collateral ligament (zone 3): macroscopic view (a) and microscopic
view (b). MCL medial collateral ligament, MM medial meniscus, JC joint capsule, 1 loos connective tissue separating medial collateral ligament from joint capsule, 2 blood vessels
13
12
Fig. 8 Anatomical dissection of zone 4 of medial meniscus (a). Menisco-tibial (coronary) ligament is marked with white arrows (b, c). Medial collateral ligament is marked with black arrows (b), notice: the level of attachment of menisco-tibial (coronary) ligament on the tibia. MM medial meniscus, MTC medial tibial condyle. His-
Fig. 9 Anatomical dissection of posterior aspect of the left knee joint. Posterior femoral recess is marked with black arrows. Notice: free superior edge of posterior horn of medial meniscus. LFC lateral femoral condyle, ML lateral meniscus, PT popliteal tendon, PCL posterior cruciate ligament, MM medial meniscus, JC joint capsule, MFC medial femoral condyle, 1 proximal attachment of lateral head of gastrocnemius muscle, 2 distal attachment of ilio-tibial band, 3 distal attachment of biceps tendon, 4 lateral collateral ligament, 5 proximal attachment of medial head of gastrocnemius muscle, 6 distal attachment of semimembranous tendon
The radiographic landmarks of the tibial attachment in the antero-posterior and lateral view are the following [7]. Anteroposterior view • 4.8 mm proximal to the proximal joint line • 2.3 mm lateral to medial tibial eminence line • 12.7 mm medial to lateral tibial eminence line
13
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14
tology (d) (light microscopy, H&E stain, original magnification ×4) of cross section of medial meniscus within zone 4. Menisco-tibial (coronary) ligament is marked with white arrows. Notice: curved shape (marked with yellow arrows) of superior edge of medial meniscus within this zone, with no attachments to surrounding tissues
Fig. 10 Anatomical dissection of left knee joint. Postero-medial femoral recess is marked with yellow arrows. MCL medial collateral ligament, MM medial meniscus, JC joint capsule, PCL posterior cruciate ligament, ACL anterior cruciate ligament, magnification of posteromedial femoral recess
Lateral view • 24.1 mm posterior to tibial long axis • 21.8 mm proximal to CGD line • 18 mm anterior to posterior tibial plateau line [7]
Connections between medial and lateral meniscus There are four different menisco-meniscal ligaments connecting the medial with the lateral meniscus [20]: the medial oblique intermeniscal ligaments; the lateral oblique intermeniscal ligaments; the anterior ligament (also called
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14
13
Fig. 11 Anatomical dissection of proximal tibial articular surface (plan view, femur removed). Tibial attachment of posterior root of medial meniscus is marked with white arrows. PCL posterior cruciate ligament, aMFL anterior menisco-femoral ligament (Humphry ligament), pML posterior root of lateral meniscus, ACL anterior cruciate ligament, aML anterior root of lateral meniscus, aMM anterior root of medial meniscus, pMM posterior root of medial meniscus, TL transverse ligament (anterior menisco-meniscal ligament), MCL medial collateral ligament
transverse ligament); and the posterior intermeniscal ligament. The transverse ligament (anterior intermeniscal or anterior menisco-meniscal ligament) is present in 60–94 % of all knees [1, 11]. In contrast, the posterior intermeniscal ligament can be found in 1–4 % of cases only [3]. The medial oblique intermeniscal ligament, which is present in 1 % of knees, takes its name from its anterior meniscal point of origin, begins from the central part of the anterior root of medial meniscus and passes obliquely backwards to the upper part of the posterior horn of the lateral meniscus. Consequently, lateral intermeniscal ligaments, which are present in 4 % of knees, extend from the anterior root of lateral meniscus, passing between the cruciates and inserting into the upper part of the posterior root of the medial meniscus. Chan et al. [3] also described two cases of unilateral menisco-meniscal ligament: lateral and medial. In those cases, there was additional connection between anterior and posterior horn of each meniscus. Both ligaments were identified on MRI, and a unilateral medial menisco-meniscal ligament was also confirmed by arthroscopy.
Clinical relevance Although meniscal surgery is one of the most frequent procedures in orthopaedics, a more detailed understanding
Fig. 12 Magnification of anatomical dissection of posterior aspect of the knee joint. Posterior root of medial meniscus is marked with white arrows. 1 posterior cruciate ligament, 2 anterior menisco-femoral ligament, 3 posterior root of lateral meniscus, 4 tibial attachment of anterior cruciate ligament, 5 anterior root of lateral meniscus
of the menisci’s anatomy is likely required to improve the success of repairs or replacements. Dividing the medial meniscus into five anatomical zones, as described here, has important implications for meniscal treatment. In each zone, a different suturing technique is required for anatomical reconstruction. Knowing the exact anatomy of zones 1 and 5—anterior and posterior root—is important especially for meniscal transplantation. In order to anatomically suture anterior and/or posterior root of medial meniscus, we need to restore rigid bone fixation through transosseous suturing. Differences of as little as 2–3 mm have a significant impact on the meniscus function [14]. The insertion of the meniscus transplant more medially will cause significant extrusion and an increase in femorotibial loading. On the other hand, the meniscus transplant becomes very vulnerable if the insertion is too close to the tibial eminentia because of overloading. Considering the attachment of the medial meniscus in zone 2a, the inferior vertical suture technique is recommended in order to restore the menisco-tibial ligament. This is slightly different in zone 2b, because of the attachment
13
14
of the inferior and superior part of the meniscus periphery. Zone 3 requires two vertical sutures from the anatomical point of view in order to restore both the menisco-tibial (coronal) and menisco-femoral ligaments. However, it might be a challenge to suture the meniscus to the joint capsule (which some authors [17] also call the deep layer of medial collateral ligament) alone, instead to the medial collateral ligament (superficial layer). The solution would be to use absorbable sutures that allow, in time, independent movement between medial collateral ligament and joint capsule. Zone 4 seems to be the most controversial. Our anatomical study showed only the attachment of the inferior part of the meniscus periphery to tibia. At the same time, this is the most challenging and technically difficult area for meniscus repair. Many surgeons are satisfied suturing this part of the meniscus to the posterior capsule, but it may have a significant impact on the mobility of the posteromedial corner. There is a wide space between outer surface of zone 4 of medial meniscus and the joint capsule. Suturing the meniscus to the joint capsule will close the recess and subsequently impair the mobility of the medial meniscus, which may significantly change the position of meniscus during knee movement. For this reason, a more anatomically suture placement in zone 4 should be considered. Acknowledgments The authors gratefully acknowledge Maciej Pronicki, MD, PhD for providing histopathology examinations, Maciej S´miarowski ([email protected]) for taking all photographs and Center for Medical Education (www.cemed.pl) for its help.
References 1. Berlet GC, Fowler PJ (1998) The anterior horn of the medial meniscus an anatomic study of its insertion. Am J Sports Med Am Orthop Soc Sports Med 26:540–543 2. Becker R, Wirz D, Wolf C, Göpfert B, Nebelung W, Friederich N (2005) Measurement of meniscofemoral contact pressure after repair of bucket-handle tears with biodegradable implants. Arch Orthop Trauma Surg 125(4):254–602 3. Chan CM, Goldblatt JP (2012) Unilateral meniscomeniscal ligament. Orthopedics 35:e1815–e1817 4. Clark CR, Ogden JA (1983) Development of the menisci of the human knee joint. Morphological changes and their potential role in childhood meniscal injury. J Bone Joint Surg Am 65:538–547
13
Knee Surg Sports Traumatol Arthrosc (2015) 23:8–14 5. Englund M (2008) The role of the meniscus in osteoarthritis genesis. Rheum Dis Clin North Am 34:573–579 6. Fenn S, Datir A, Saifuddin A (2009) Synovial recesses of the knee: MR imaging review of anatomical and pathological features. Skelet Radiol 38:317–328 7. James EW, LaPrade CM, Ellman MB, Wijdicks CA, Engebretsen L, LaPrade RF (2014) Radiographic identification of the anterior and posterior root attachments of the medial and lateral menisci. Am J Sports Med 42:2707–2714 8. Johannsen AM, Civitarese DM, Padalecki JR, Goldsmith MT, Wijdicks CA, LaPrade RF (2012) Qualitative and quantitative anatomic analysis of the posterior root attachments of the medial and lateral menisci. Am J Sports Med 40:2342–2347 9. LaPrade CM, Ellman MB, Rasmussen MT, James EW, Wijdicks CA, Engebretsen L, LaPrade RF (2014) Anatomy of the anterior root attachments of the medial and lateral menisci: a quantitative analysis. Am J Sports Med 42:2386–2392 10. Lougher L, Southgate CR, Holt MD (2003) Coronary liga ment rupture as a cause of medial knee pain. Arthroscopy 19:e157–e158 11. Masouros SD, McDermott ID, Amis AA, Bull AM (2008) Biomechanics of the meniscus-meniscal ligament construct of the knee. Knee Surg Sports Traumatol Arthrosc 16:1121–1132 12. Rainio P, Sarimo J, Rantanen J, Alanen J, Orava S (2002) Observation of anomalous insertion of the medial meniscus on the anterior cruciate ligament. Arthrosc J Arthrosc Relat Surg 18:1–6 13. Rath E, Richmond JC (2000) The menisci: basic science and advances in treatment. Br J Sports Med 34:252–257 14. Stärke C, Kopf S, Gröbel KH, Becker R (2010) The effect of a nonanatomic repair of the meniscal horn attachment on meniscal tension: a biomechanical study. Arthroscopy 26:358–365 15. Stein T, Mehling AP, Welsch F, von Eisenhart-Rothe R, Jäger A (2010) Long-term outcome after arthroscopic meniscal repair versus arthroscopic partial meniscectomy for traumatic meniscal tears. Am J Sports Med 38:1542–1548 16. Tardieu C, Dupont JY (2001) The origin of femoral trochlear dysplasia: comparative anatomy, evolution, and growth of the patellofemoral joint. Rev Chir Orthop Reparatrice Appar Mot 87:373–383 17. Weiss CB, Lundberg M, Hamberg P, DeHaven KE, Gillquist J (1989) Non-operative treatment of meniscal tears. J Bone Joint Surg Am 71:811–822 18. Wymenga AB, Kats JJ, Kooloos J, Hillen B (2006) Surgical anatomy of the medial collateral ligament and the posteromedial capsule of the knee. Knee Surg Sports Traumatol Arthrosc 14:229–234 19. Yagishita K, Muneta T, Ogiuchi T, Sekiya I, Shinomiya K (2004) Healing potential of meniscal tears without repair in knees with anterior cruciate ligament reconstruction. Am J Sports Med 32:1953–1961 20. Zivanović S (1974) Menisco-meniscal ligaments of the human knee joint. Anat Anz 135:35–42
