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Knee joint ligaments
Medical expert of the article
Conditionally, all the stabilizers are divided into two groups, as was previously accepted, but three: passive, relatively passive and active. Passive elements of the stabilizing system include bones, the synovial capsule of the joint, to the relatively passive ones - menisci, ligaments of the knee joint, fibrous capsule of the joint, to the active ones - muscles with their tendons.
Relatively passive elements involved in stabilizing the knee joint include those that do not actively shift the tibia relatively femur but have a direct link to ligaments and tendons (for example, menisci) or are themselves ligamentous structures that have a direct or indirect relationship with muscles.
Functional anatomy of the capsular-ligamentous knee apparatus
In the joint up to 90 °. The role of the secondary stabilizer ZKS gets for external rotation of the tibia at 90 ° flexion, however it plays a smaller role with full extension of the tibia. D. Veltry (1994) also notes that ZKS is a secondary stabilizer for varus calf variance.
BCS is the primary stabilizer of the calf valgus deviation. It is also the primary limiter of the external rotation of the tibia. The role of BCS as a secondary stabilizer is to limit the anterior displacement of the tibia. Thus, with intact PKC, the intersection of BCS will not give a change in the front translation of the tibia. However, after damage to the PKC and the intersection of BCS, there is a significant increase in the pathological displacement of the tibia anteriorly. In addition to BCS, the medial section of the joint capsule also somewhat restricts the shin displacement anteriorly.
ISS is the primary stabilizer of varus calf variation and its internal rotation. The post-lateral section of the joint capsule is a secondary stabilizer.
Attaching the ligaments of the knee joint
There are two types of attachment: direct and indirect. The direct type is characterized by the fact that most of the collagen fibers penetrate directly into the cortical bone at the point of attachment. Indirect type is determined by the fact that a significant amount of collagen fibers at the entrance continues into periosteal and fascial structures. This type is characteristic for significant length of attachment to the bone. An example of a direct type is the femoral attachment of the medial collateral ligament of the knee joint, where the transition from the bending of the strong ligament to the rigid cortical plate is performed through four-walled structures, namely knee joints, unmineralized fibrous cartilage, mineralized fibrous cartilage, cortical bone. An example of a different type of attachment within a single ligament structure is the tibial attachment of PKC. On the one hand, there is a large common indirect attachment, where most of the collagen fibers continue in the periosteum, and on the other - there are some fibrous-bony transitions with the direct entry of collagen fibers into the bone.
Isometrics - maintaining a constant length of the ligament of the knee joint with articulations. In the hinge joint, with a range of 135 ° movements, the notion of isometrics is extremely important for a correct understanding of its biomechanics in norm and pathology. In the sagittal plane, movements in the knee joint can be characterized as the union of four components: two cruciate ligaments and bone bridges between their divergences. The most complex arrangement is in the collateral ligaments, which is due to the lack of complete isometry during articulations at various angles of flexion in the ridge.
Cruciate ligament of knee joint
Cross-shaped ligaments of the knee joint are supplied from the median artery. Total innervation is from the nerves of the popliteal plexus.
The anterior cruciate ligament of the knee joint is a connective tissue cord (average 32 mm long, 9 mm wide) that is directed from the posterior inner surface of the femoral condyles external to the posterior fistula on the tibia. The normal SCS has an inclination angle of 27 ° at 90 ° flexion, the rotational component of the fibers at the attachment points on the tibial and femur bones is 110 °, the angle of the intracellular twisting of the collagen fibers ranges from 23 to 25 °. With complete extension of the fiber, PKCs run approximately parallel to the sagittal plane. There is a slight rotation of the ligament of the knee joint with respect to the longitudinal axis, the shape of the tibial oval is longer, longer in the anteroposterior direction than in the medial lateral.
The posterior cruciate ligament of the knee joint is shorter, more durable (average length 30 mm) and starts from the medial femoral condyle, the shape of the divergence is semicircular. It is longer in anteroposterior direction in its proximal part and has the appearance of a curved arch in the distal part on the femur. A high femoral attachment gives the ligament an almost vertical course. Distal attachment of ZKS is located directly on the posterior surface of the proximal end of the tibia.
A narrow, anteromedial bundle is extracted in the PKC, which is stretched during bending and a wide posterolateral bundle having a fiber tension during extension. VZKS allocate a wide anterolateral bundle, stretching when flexing the tibia, a narrow postromedial bundle that undergoes tension at the extension and various forms of the meniscofemoral cord, tense at flexion.
However, it is rather a conditional division of the bundles of cruciate ligaments of the knee joint with respect to their tension in flexion-extension, since it is clear that because of their close functional relationship there are absolutely no isometric fibers. Special attention should be paid to the work of a number of authors on the cross-sectional anatomy of the cruciate ligaments, which showed that the cross-sectional area of the SCS is 1.5 times larger than ICS (statistically reliable data were obtained in the femoral attachment and mid-ligament of the knee joint). The cross-sectional area does not change when moving. The cross-sectional area of the ZKS is increased from the tibia to the femoral, and the VIC on the contrary - from the femoral to the tibial. The meniscofemoral ligament of the knee joint is 20% v / v of the posterior cruciform cruciate ligament of the knee joint. ZKS is divided into anterolateral, postromedial, meniscofemoral parts. We are impressed by the conclusions of these authors, since they are consonant with our understanding of this problem, namely:
- Reconstructive surgery does not restore a three-component complex of ZKS.
- The anterolateral beam of ZKS is twice as long as the postoperiodial and plays an important role in the kinematics of the knee joint.
- The meniscofemoral portion is always present, has similar cross-sectional dimensions with the post-merodial bundle. Its position, size and strength play a significant role in the control of the posterior and posterolateral shin-to-hip mixing.
Further analysis of the functional anatomy of the knee joint is more advisable to produce an anatomical area, since there is a close functional relationship between the passive (capsule, bone) and the active components of stability (muscle).
Medial capsular and ligament complex
In practical terms, it is convenient to divide the anatomical structures of this department into three layers: deep, medium and superficial.
The deepest third layer includes the medial joint capsule, thin in the anterior section. Its length is not large, it is located under the inner meniscus, providing its stronger attachment to the tibia than to the femur. The middle part of the deep layer is represented by a deep leaf of the medial collateral ligament of the knee joint. This segment is divided into menisco-femoral and meniscotibial parts. In the posteromedial section, the middle layer (II) merges with the deeper (III). This area is called the back oblique bunch.
In this case, a close fusion of passive elements with relatively passive ones is clearly visible, which indicates the conventionality of such a division, although it contains a certain biomechanical meaning.
The meniscofemoral parts of the ligament of the knee joint further back become thinner and have the least tension when flexing in the joint. This area is strengthened by the tendon m. Semimembranosus. A part of the tendon fibers is weaved into the oblique popliteal ligament, which extends transversely from the distal part of the medial surface of the grove bone to the proximal part of the lateral condylar femur in the forward direction to the posterior portion of the joint capsule. Tendon m. Semimembranosus also gives fibers anteriorly into the posterior oblique ligament and into the medial meniscus. Third portion m. The semimembranosus is attached directly to the posterior invertebral bone surface. In these areas the capsule is markedly thickened. The other two heads m. Semimembranous attach to the medial surface of the sternum, passing deeply (relative to BCS) to the layer that is associated with m popliteus. The most powerful part of layer III is the deep BCS sheet, which has fibers oriented parallel to, similar to PKC fibers with full extension. At maximum flexion, the attachment of the ligament of the knee is stretched anteriorly, causing the ligament to go almost vertically (i.e., perpendicular to the tibial plateau). Vigorous attachment of a deep batch of BCS lies distally and somewhat posteriorly with respect to the superficial layer of the ligament of the knee joint. The surface sheet of BCS extends longitudinally in the intermediate layer. When folded, it remains perpendicular to the surface of the tibial plateau, but shifts as the femur moves.
Thus, there is a clear interconnection and interdependence of the activity of various bundles of BCS. So, in the flexion position, the front fibers of the ligament of the knee joint strain, while the hind legs relax. This led us to the conclusion that with conservative treatment of BCS ruptures, depending on the localization of damage to the ligament of the knee joint, to maximally reduce the diastase between broken fibers, it is necessary to select the optimal bending angle in the knee joint. When surgical treatment, suturing the ligaments of the knee joint in the acute period should also be made, if possible, taking into account these biomechanical features of BCS.
The back portions of the II and III layers of the joint capsule are connected in the posterior oblique ligament. The femoral origin of this ligament of the knee joint lies on the medial surface of the femur behind the start of the BCS surface sheet. Fibers of the ligament of the knee joint are directed back and down and are attached to the region of the posteromedial angle of the articular end of the tibia. The meniscus-tibial part of this ligament of the knee joint is very important in attaching the back of the meniscus. The same area is an important attachment of m. Semimembranosus.
Until now, there is no consensus as to whether the back oblique ligament is a separate ligament, or it is the posterior portion of the BCS surface layer. If the PKC is damaged, this area of the knee joint is a secondary stabilizer.
The medial collateral ligamentous complex carries out the restriction of excessive valgus deviation and external rotation of the tibia. The main active stabilizer in this area are tendons of the muscles of the large "goose paw" (pes anserinus), which cover BCS with full extension of the shin. BCS (deep portion), in conjunction with the SCC, also imposes a restriction on the front shank mixing. Back of BCS. The posterior oblique ligament strengthens the posterior medial joint.
The most superficial I layer consists of the continuation of the deep fascia of the thigh and the tendon stretch m. Sartorius. The fibers of layers I and II become inseparable in the anterior section of the surface part of BCS. Dorsal, where the II and III layers are inseparable, the tendons m. Gracilis and m. The scmitendinosus lie on top of the joint, between the I and II layers. In the posterior part the capsule of the joint is thinned and consists of one layer, with the exception of hidden discrete thickenings.
Lateral capsular-ligament complex
The lateral section of the joint also consists of three layers of ligamentous structures. The joint capsule is divided into the anterior, middle, posterior sections, as well as the meniscofemoral and meniscotibial parts. In the lateral part of the joint there is an intracapsular tendon of popliteus, which goes to the peripheral attachment of the lateral meniscus and is attached to the lateral section of the joint capsule, in front of m. Popliteus contains a. Geniculare inferior. There are several thickenings of the deepest layer (III). ISS - dense strands of longitudinal collagen fibers, lying freely between two layers. This ligament of the knee is located between the fibula and the external condyle of the femur. The femoral extraction of the ISS lies on the lumbnail, connecting the entrance of the tendon m. Popliteus (distal end) and the beginning of the lateral head m. Gastrocnemius (proximal end). Somewhat posteriorly and most deeply there is lg. The arcuatum, which starts from the fibular head, enters the posterior capsule next to the lg. Obliquus popliteus. Tendon m. Popliteus functions like a bunch. M. Popliteus produces an internal rotation of the tibia with an increase in flexion of the tibia. That is, it is more a rotator of the lower leg than a flexor or extensor. The ISS is the stop of the pathological varus deviation, despite the fact that it relaxes when bent.
The superficial spore (I) on the lateral side is the continuation of the deep fascia of the thigh that surrounds the tractus iliotibialis anterolateral and the tendon m. Biceps femoris posterolaterally. Intermediate layer (II) is the tendon stretch of the patella, which starts from the orotibial tract and the capsule of the joint, passes medially and attaches to the patella. Tractus iliotibialis assists the ISS in lateral joint stabilization. There is a close anatomical and functional relationship between either the oribial tract and the intermuscular septum when approaching the attachment site at the Gerdy hillock. Muller \ V. (1982) designated this as an anterolateral tibiofemoral ligament, playing the role of a secondary stabilizer that limits the anterior displacement of the tibia.
There are also four ligamentous structures: lateral and medial meniscopatellar ligaments of the knee joint, lateral and medial patellofemoral ligaments of the knee joint. However, in our opinion, this division is rather conditional, since these elements are part of other anatomical and functional structures.
A number of authors distinguish a part of the tendon m. Popliteus as a ligamentous structure. Popliteo-fibulare, since this ligament of the knee joint along with lg. Arcuaium, ISS, m. Popliteus. Supports ZKS in control of posterior shank displacement. Different articulating structures, for example, the fat pad, the proximal tibiofibular joint, are not considered here, since they are not directly related to the stabilization of the joint, although their role as certain passive stabilizing elements is not excluded.
Biomechanical aspects of the development of chronic post-traumatic knee instability
Non-contact methods of measurement of joint movements in biomechanical testing were applied by J. Perry D. Moynes, D. Antonelli (1984).
Electromagnetic devices for the same purposes were used by J. Sidles et al. (1988). A mathematical modeling for the processing of information on motion in the knee joint is proposed.
Movement in the joints can be represented as a variety of combinations of translations and rotations, which are controlled by several mechanisms. There are four components that affect the stability of the joint, contributing to the retention of the articulating surfaces in contact with each other: passive structures of soft tissues, such as the cruciform and collateral ligaments of the knee joint, menisci, which act either directly by stretching the corresponding tissues, restricting movements in the tibial - a hip joint or indirectly, creating a compression load on the joint; active muscle forces (active dynamic components of stabilization), such as the traction of the quadriceps muscle of the hip, the posterior group of the hip muscles, whose mechanism of action is associated with the limitation of the amplitude of movements in the joint and the transformation of one movement into another; external impact on the joint, for example moments of inertia arising during locomotion; geometry of articulating surfaces (absolutely passive elements of stability), limiting movements in the joint due to congruence articulating articular surfaces of bones. There are three translational degrees of freedom of movement between the tibia and the femur, described as anteroposterior, medial-lateral and proximal-distal; and three rotational degrees of freedom of movement, namely: flexion-extensia, valius-varus and external-internal rotation. In addition, there is a so-called automatic rotation, which is determined by the form of the articulating surfaces in the knee joint. Thus, when the shin is unbent, its external rotation takes place, its amplitude is low and on average is 1 °.
Stabilizing role of ligaments of the knee joint
A number of experimental studies have allowed a more detailed study of the function of ligaments. The method of selective partitioning was used. This allowed us to formulate the concept of primary and secondary stabilizers in normal and with damage to the ligaments of the knee joint. A similar proposal was published by us in 1987. The essence of the concept is as follows. The ligament structure, which provides the greatest resistance to anteroposterior dislocation (translation) and rotation, which occurs under the influence of external force, is considered the primary stabilizer. Elements that provide a smaller contribution to the resistance at external load - secondary limiters (stabilizers). The isolated intersection of primary stabilizers leads to a significant increase in translation and rotation, which this structure restricts. At the intersection of secondary stabilizers there is no increase in pathological displacement with the integrity of the primary stabilizer. In case of sectional damage to the secondary and rupture of the primary stabilizer, a more significant increase in the abnormal displacement of the tibia relative to the femur occurs. The ligament of the knee joint can act as the primary stabilizer of certain translations and rotations and simultaneously secondarily restrict other movements in the joint. For example, BCS is the primary stabilizer for valgus abnormality of the tibia, but also acts as a secondary limiter for anterior tibial displacement relative to the thigh.
The anterior cruciate ligament of the knee joint is the primary limiter of the anterior tibial displacement at all bending angles in the knee joint, taking about 80-85% of the counteraction to this movement. The maximum value of this restriction is noted at 30 ° flexion in the joint. Isolated PCS partitioning leads to greater translation at 30 ° than at 90 °. PKC also provides a primary limitation of the medial bias of the tibia with full extension and 30 ° flexion in the joint. The secondary role of PKC as a stabilizer is to limit the rotation of the tibia, especially when fully extended, being a great deterrent for internal rotation, rather than external. However, some authors point out that insignificant rotational instability arises in the case of isolated damage to the SCP.
In our opinion, this is due to the fact that both PKC and ZKS are elements of the central axis of the joint. The magnitude of the arm of the force for the lever of the PKS influence on the rotation of the tibia is extremely small, practically absent in the ZKS. Therefore, the impact on the limitation of rotational movements from the cruciate ligament is minimal. Isolated intersection of PKC and posterolateral structures (m. Popliteus tendons, ISS, lg. Popliteo-fibulare) leads to an increase in anterior and posterior shank bias, variance and internal rotation.
Active dynamic components of stabilization
In the studies devoted to this issue, more attention is paid to the action of muscles on passive ligamentous elements of stabilization by tension or relaxation at certain angles of flexion in the joint. Thus, the quadriceps muscle of the femur has the greatest effect on the cruciate ligaments of the knee joint when flexing the tibia from 10 to 70 °. The activation of the quadriceps femoris leads to an increase in the tension of the PKC. On the contrary, the tension of the LCS decreases in this case. The muscles of the posterior femoral group (hamstring) somewhat reduce the tension of the PKC when bending more than 70 °.
To ensure consistency in the presentation of the material, we will briefly repeat some data, which were discussed in detail in the previous sections.
In more detail, the stabilizing function of the capsular-ligament structures and periarticular muscles will be considered a little later.
What mechanisms ensure the stability of such a complex system in the static and dynamic?
At first glance, forces that balance each other in the frontal plane (valgus-varus) and sagittal (front and back mixing) work here. In reality, the knee joint stabilization program is much deeper and is based on the concept of torsion, that is, the spiral model lies at the base of its stabilization mechanism. 'Hack, the inner rotation of the tibia is accompanied by its valgus deviation. The outer articular surface moves more than the inner surface. Starting motion, the condyles in the first degrees of flexion slide in the direction of the axis of rotation. In the flexion position with valgus deviation and external rotation of the tibia, the CS is much less stable than in the flexion position with varus deviation and internal rotation.
In order to understand this, let us consider the shape of articular surfaces and the conditions of mechanical loading in three planes.
The forms of articular surfaces of the femoral and tibia are discognorant, that is, the convexity of the first is greater than the concavity of the second. Menisci make them congruent. As a result, in fact, there are two joints - menisco-femoral and mispik-tibial. When bending and unbending in the menisco-femoral section of the copilla, the upper surface of the meniscus touches the posterior and lower surfaces of the condyles of the femur. Their configuration is such that the back surface forms an arc of 120 ° with a radius of 5 cm, and the lower one - 40 ° with a radius of 9 cm, that is, there are two centers of rotation and, when bending, one replaces the other. In fact, the condyles curl in the form of a spiral and the radius of curvature increases all the time in the posterior front direction, and the previously mentioned rotation centers correspond only to the end points of the curve along which the center of rotation moves during flexion and extension. Lateral ligaments of the knee joint originate in the places corresponding to the centers of its rotation. As the extension of the ligament knee joint stretch.
In the menisco-femoral part of the knee joint, flexion and extension occur, and in the meniscus and tibial bone surfaces formed by its meniscus-tibial section, rotational motions occur around the longitudinal axis. The latter are possible only with the bent position of the joint.
When flexing and unbending, the meniscus also moves in the anteroposterior direction along the articular surfaces of the tibia: when bending the meniscus along with the femur, they move backwards, and when they are bent, they move backwards, that is, the meniscus-tibial joint is movable. The movement of menisci in the anteroposterior direction is due to the pressure on them of the condyles of the femur and is passive. However, the pull of the tendon of the semimembranous and popliteal muscle causes some of their displacement back.
Thus, it can be concluded that the articular surfaces of the knee joint are discongrugent, they are strengthened by capsular-ligamentous elements, which are acted upon by forces directed in three mutually perpendicular planes.
The central core (pivot central) of the knee joint, ensuring its stability, are the cruciform ligaments of the knee joint, which mutually complement each other.
The anterior cruciate ligament originates on the inner surface of the external condyle of the femur and terminates in the anterior section of the intercondylar elevation. Three bundles are distinguished in it: the posterior, front and inner. When bending 30 °, the front fibers are stretched more than the rear fibers, they are stretched equally at 90 °, and at 120 ° the back and outer fibers are stretched more than the front fibers. With full extension with external or internal rotation of the tibia, all fibers are also stretched. At 30 ° with the internal rotation of the tibia, the anteroneous fibers are strained, and the posterolateral ones are relaxed. The axis of rotation of the anterior cruciate ligament of the knee joint is located in the posterior part.
The posterior cruciate ligament originates on the external surface of the inner condyle of the femur and terminates in the posterior part of the intercondylar tibial elevation. It distinguishes four beams: anterior, anterior, meniscus-femoral (Wrisbcrg) and strongly forward, or a bundle of Humphrey. In the frontal plane, it is oriented at an angle of 52-59 °; in the sagittal - 44-59 ° - This variability is due to the fact that it performs a dual role: when flexing, the fore stretches, and when they are extended, the back fibers are stretched. In addition, the rear fibers participate in the passive counteracting rotation in the horizontal plane.
With valgus deviation and external rotation of the tibia, the anterior cruciate ligament restricts the forward displacement of the medial part of the tibial plateau, and the posterior one - the posterior displacement of the lateral part of the tibia. With valgus deviation and internal rotation of the tibia, the posterior cruciate ligament restricts the posterior displacement of the medial part of the tibial plateau, and the anterior one - the anterior dislocation of the medial lobe.
When the flexor muscles and flexor extensor muscles are stressed, the tension of the anterior cruciate ligament of the knee joint changes. Thus, according to the data of P. Renstrom and SW Arms (1986), with a passive flexion from 0 to 75 °, the tension of the ligament of the knee joint does not change, with an isometric tension of the isochio-torsional muscles, the anterior displacement of the tibia decreases (the maximum of the effect is between 30 and 60 °) , the isometric and dynamic tension of the quadriceps muscle is accompanied by the tension of the ligament of the knee joint, usually from 0 to 30 ° of flexion, the simultaneous stress of the flexors and extensors of the tibia does not increase its tension at a flexion angle of less than 45 °.
On the periphery, the knee joint is bounded by a capsule with its thickenings and ligaments, which are passive stabilizers, counteracting excessive shocks in the anteroposterior direction, its excessive deviation and rotation, in various poses.
The medial lateral or tibial collateral ligament consists of two fascicles: one is a superficial ligament located between the tubercle of the femoral condyle and the inner surface of the tibia, and the other is a deep, wider, extending front and posterior from the superficial fascia. The posterior and oblique deep fibers of this ligament of the knee are stretched when bent from 90 ° to fully extend. The tibial collateral ligament retains the tibia from excessive valgus deviation and external rotation.
Behind the tibial collateral ligament of the knee joint, there is a concentration of fibers called the inferior fibro-tendon nucleus (noyau fibro-tendineux-postero-interne) or the posterior internal angular point (point d'angle postero-inteme).
The outer lateral or peroneal collateral ligament is classified as extra-vaginal. It starts from the tubercle of the external condyle of the femur and is attached to the fibular head. The function of this ligament of the knee joint is to keep the shin from excessive varus deviation and internal rotation.
Behind is the fibello-fibular ligament, which starts from the facial and is attached to the fibular head.
Between the two ligaments is located the posterior-fibrous-tendon nucleus (noyau fibro-tendmeux-postero-externe) or the posterior internal point (point d'angle postero-externe), formed by the attachment of the popliteal tendon and the most external fibers of the capsule thickenings (the outer arch of the popliteal arch or ligaments of the knee joint).
The posterior ligament plays an important role in limiting passive extension. It consists of three parts: middle and two lateral. The middle part is connected with the stretching of the oblique popliteal ligament of the knee joint and the terminal fibers of the semimembranous muscle. Making a passage to the popliteal muscle, the arch of the popliteal ligament of the knee joint with its two beams complements the posterior median structures. This arch strengthens the capsule only in 13% of cases (according to Leebacher), and the fibellus-peroneal ligament - in 20%. There is an inverse relationship between the significance of these non-permanent ligaments.
The pterygoid ligaments of the knee joint, or the patellar restorers, are formed by a number of capsular-ligament structures - the own femoral-patellar, oblique and intersecting fibers of the outer and inner broad thigh muscles, oblique fibers of the wide fascia of the thigh and aponeurosis of the sartorius muscle. The variability of the direction of the fibers and the intimate connection with the surrounding muscles, which, when contracted, can pull them, explain the ability of these structures to perform the function of active and passive stabilizers, analogous to the cruciform and collateral ligaments.
Anatomical foundations of knee rotational stability
Fibro-tendon periarticular nuclei (les noyaux fibro-tendineux peri-articulaires) between zones of thickening of the joint capsule are represented by ligaments, among which four fibrous-tendinous nuclei are distinguished, in other words, different sections of the capsule and active muscle-tendon elements are distinguished. Four fibrous-tendon I / fa divide into two anterior and two posterior.
The internal fibrotic tendon nucleus is located in front of the tibial collateral ligament of the knee joint and includes fibers of its deep fascicle, femur-patellar and internal meniscus-patellar ligament; the tendon of the sartorius muscle, the fine muscle, the oblique portion of the semimembranous muscle tendon, the oblique and vertical fibers of the tendon part of the wide thigh muscle.
The internal fibrinous tendon nucleus is located behind the surface bundle of the tibial collateral ligament of the knee joint. In this space, a deep bundle of the said ligament of the knee joint is distinguished, an oblique bundle extending from the condyle, attachment of the inner head of the gastrocnemius muscle, and a straight and recurrent bundle of the tendon of the semimembranous muscle.
The anteriorly fibrous-tendinous nucleus is located in front of the peroneal collateral ligament and includes an articular capsule, the femur-patellar and external meniscus-patellar ligament of the knee joint, oblique and vertical muscle fibers tensing the broad fascia of the thigh.
The anterior-posterior fibrous-tendon nucleus is located behind the peroneal collateral ligament of the knee joint. It consists of the tendon of the popliteal muscle, the fibello-fibular tendon, the most surface of the fibers coming from the condyle with the fibers of the external part (arch) of the popliteal arch (ligament of the knee joint), the attachment site of the external head of the gastrocnemius muscle and the tendon of the biceps femoris.