Cruciate ligament

The cruciate ligaments (Latin: Ligamenta cruciata genus) include, in addition to the lateral ligament ( fibular collateral ligament ) and the medial collateral ligament ( tibial collateral ligament ) to the ligaments of the knee joint of mammals. They cross in the center of the knee joint, giving them their name. Your job is, along with the other structures of the knee ligaments which stabilize the joint with every movement.

Anatomy

Strictly and purely anatomically are the cruciate ligaments in the knee joint not, but outside of the joint surfaces ( extra-articular ). This is justified by the fact that they are bounded by the synovial membrane bag ( synovial sac ) at the articular surfaces down. This synovial sac encloses with its outside, only the anterior and lateral portions of the cruciate ligaments, therefore, we speak of retrosynovialer location. In evolutionary terms, it has been found that the cruciate ligaments from behind radiate into the hinge region and not vice versa, which explains their location outside of the synovial membrane.

Structure

The cruciate ligaments consist, like other joints accompanying tapes also, from taut, collagenous fiber tracts. They are parallel to one another in the so-called fiber bundles that are loosely connected to each other by connective tissue. Where they attach to bone ( insertion), changed its fiber structure and arrangement in the direction of the periosteum ( periosteal ), which also consists of very tight collagen fibers, however, are highly crosslinked. Your blood supply, they get especially from the genus A. media.

Location and History

Anterior cruciate ligament

If you open a knee joint from the front, so you can see that the cruciate ligaments are housed centrally in the joint. The anterior cruciate ligament ( cruciate ligament anterior, VKB or LCA or ACL) is the front - middle area of the knee joint ( anterior intercondylar area ) at the two cartilage free cruciate ligament bumps ( tubercle of intercondylar medial / lateral tibial ) of the tibial head (caput tibiae ) fixed. This increased area between the two articular surfaces of the tibia intercondylar eminence is called the head. This is where not only the anterior cruciate ligament, but also fibrous bands of the two menisci. The band draws from the front - bottom - inside ( anterior caudal - medial) in the depression between the condyles ( intercondylar notch femoris ) backward - upward-outward ( dorso- cranial - lateral). There inserted (Insertion of bony ingrowth = of tendons and ligaments ) is at the rear of the side facing the middle surface of the outer femoral Gelenkknorrens ( lateral femoral condyle ) at the cartilage - bone border. This course is colloquially referred to as " pocket- shaped".

There are three band parts are distinguished:

• A front - inside ( anteromedial ) bundle. This has the longest fibers of the entire anterior cruciate ligament. For insight into the knee joint from the front it becomes visible first. It greatly tightens especially in knee flexion (flexion ). With an injury of the anterior cruciate ligament, it is the share of tears most likely.
• A rear - outer ( posterolateral ) bundle. This is covered by the anteromedial bundle and has its voltage maximum at knee extension (extension). For partial band cracks it usually remains intact.
• An intermediate ( intermediate ) bundle.

The fibers have different lengths from 18.5 to 33.5 mm. For each insertion to the femur and tibia, the bundle fan out, which increases the area of fixation. Overall, the band is stretched and the individual bundles easily swallowed spiral, which is why the band towards the center as nearly round, thick structure can be seen. Some fiber trains do not advertise on the bone, but pull to the front medial meniscus band, with whom she then grow together into the bone.

Posterior cruciate ligament

Behind the anterior cruciate ligament, the posterior cruciate ligament appears ( posterior cruciate ligament, or PCL LCP, in clinical practice often PCL, Eng. Posterior cruciate ligament ). It crosses the anterior cruciate ligament at an angle of about 90 ° with the knee flexed. It is stronger and provides a total of the strongest ligaments ( ligamentous ) structure of the knee joint dar. It's in the back ( dorsal) area of the site between the condyles of the tibia ( posterior intercondylar area ) at the head of the tibia, but not as the anterior cruciate ligament on the tibial plateau, but at the trailing edge ( approximately 10 mm, starting below the articular surfaces ) fixed. The fixed point of the tibia is therefore far behind the posterior horns of the inner and outer meniscus. The band draws from the rear - bottom - outside ( dorso- caudal -lateral ) to front, top and inside ( antero- cranial - medial) in the full depth of the pit between the condyles ( condyles ) of the femur. It inserted there in the inner region of the cartilage - bone interface of the inner Gelenkknorrens ( medial femoral condyle ). With a 90 ° flexed knee could, looking from the inside, see the fan-shaped insertion of 12 clock until 4 or 5 clock.

There are two belt parts can be distinguished:

• A rear - inner ( posteromediales ) bundle (PM- bundle), which on the shin back has the innermost and the femoral condyle and thus the deepest farthest ( with the knee ) starting point. The PM bundle reaches its maximum voltage at full extension of the knee joint.
• A front - outer ( anterolateral ) bundle ( bundle - AL ), which runs from the shin to the highest and therefore the foremost approach to the femur. The AL bundle spanned fully at about 90 ° flexion of the knee joint.

Not infrequently, the posterior cruciate ligament is accompanied by one or two irregularly occurring bands, which have long been considered an integral part of the posterior cruciate ligament: the more common rear meniskofemorale ligament ( meniscofemorale posterior, Wrisberg ligament ), which together with the band of the lateral meniscus posterior horn of the tibia inserted, and the somewhat rarer front meniskofemorale ligament ( anterior meniscofemorale, Humphry 's ligament ). In fact, both are not physiologically adherent to the fiber tracts of the cruciate ligament and also do not change the overall structure of the actual posterior cruciate ligament, which is why they must not be seen as a cross-band component, but as anatomically irregularly present additional stabilization.

The tibial insertions of the cruciate ligaments of Wrisberg and band

Orientation of the cruciate ligaments

In a perspective view, the cruciate ligaments actually intersect. In the sagittal plane, they are crossed, the anterior cruciate ligament runs obliquely upwards and backwards, while the posterior cruciate ligament obliquely upwards and is aligned front ( the anterior cruciate ligament runs laterally to the posterior cruciate ligament over). Also in the frontal plane is crossed their course: your attachments to the tibia lie on a sagittal axis, while the fixed points are approximately 17 mm apart on the femur. Consequently, the posterior cruciate ligament runs obliquely upward - centered ( cranial - medial), the anterior cruciate ligament obliquely upward and sideways ( cranial - lateral). In the transverse plane, however, they are parallel to each other, their axial surfaces touch. The cruciate ligaments cross over not only themselves, but also the jeweilis opposite ipsilateral side band ( Collateral ). As the anterior cruciate ligament crosses the side band of the fibula and the posterior cruciate ligament of the tibia. Looking at the four bands from the center to the side or vice versa it is found that they are oriented obliquely to each other alternately. The collateral and cruciate ligaments intersect ( projected view) at each position of the joint in a point; the point of intersection corresponds to the instantaneous center of rotation.

The two cruciate ligaments have a differently inclined course. With the knee, the anterior cruciate ligament is more vertical, the posterior cruciate ligament more horizontally oriented, which is consistent with the orientation of the Insertionsfelder. The field of the posterior cruciate ligament is horizontal, the anterior cruciate ligament is vertical.

If the knee bent, then the horizontally disposed in the extended position posterior cruciate ligament is on vertically. It describes in relation to the tibia and an arc of more than 60 °, while the position of the anterior cruciate ligament changed little.

The length ratio between the cruciate ligaments is individual. The distance between the fixed points of the tibia and femur is characteristic for each knee, as these, inter alia, determine the profile of the trochanter.

Function

The cruciate ligaments hold together with the side bands along the knee joint. They limit the extension of the tibia, the joint lead during movement and thus give it the necessary stability. The lateral stability of the two sidebands prevents bow-legged ( genu varum ) or a knock-knee ( genu valgum ). Thus they represent the central component in the proprioceptive control loop of the knee joint dar.

The cruciate ligaments are the central elements of the knee joint passive leadership. Due to their location to each other and their mode of fixation of the femur and tibia form a four-bar chain, forcing the femur head during the bending into a rolling-sliding mechanism ( Athrokinematik or Osteokinematik ), which is - in addition to other mechanisms, - to enable a to move large swivel head on a much smaller socket physiologically. When damage to the anterior cruciate ligament this is severely disturbed and leads to cartilage and meniscus damage. The cruciate ligaments provide next to the contact pressure of the two joint partners, inter alia for a stabilization displaceable forwards and backwards. They lie so that in almost all positions of the knee joint parts of them are curious; they prevent, especially in the vulnerable unstable flexion, in which the sidebands limp, a front and rear shift of intercommunicating ( articulating ) surfaces. The collateral ligaments are tightened by the spiral shape of the trochanter of the femur in extension, because the distance between the origin and insertion becomes longer. In diffraction they are loosely analogous to the stable or unstable joint surface shape in extension and flexion. Had the trochanter of the femur around, so the radius in each diffraction angle would be the same length and the bands would move at a constant voltage. Thus, the extended knee is stable, bent it is mobile and relieved. The anterior cruciate ligament limits the stretch ( extension) of the knee joint. In the stretching direction while the rear - lateral and intermediate bundles are most excited to see while in flexion direction ( flexion), the front - center bundle is more taut. The posterior cruciate ligament prevents a straight rear displacement (translation ) of the tibial head. They also limit the extension direction of its stability and strong fibers, the rotational movement ( rotational movement ) of the lower leg, in particular the rotational movement to the inside.

Rotating the thigh bone and the lower leg to the outside to the inside ( that is, a rotational movement of the tibia to the inside), the cruciate ligaments are stretched. You will loop around each other and reinforced pull on so while they roll back and relax during the rotational movement to the outside.

The rotation axis must pass through the medial meniscus, because it is adherent to the inner side band and thus can not slide. Strained ligaments are the prerequisite for a good joint stabilization. Through the alternating change of flexion and extension of supply and Entschraubung the bands are alternately placed under train and unloaded again. Train and relief optimize the structural organization within the bands and promote metabolism. Forces applied to strained ligaments, are less than those that meet with loose ligaments. (Example: .. . During football games the knee joint gets a blow from the side, the applied force is transmitted primarily on the tapes Are these taut, they take on the power and forward them But if they are loose, the force of the blow causes only once a jerky tensioning the belts. force = mass times acceleration - Newton's second law, the law of acceleration - this is the physical formula the force that pulls on the tape is stronger ).

Cruciate ligament

Cruciate ligament injuries occur mostly due to indirect violence. From a tear ( rupture) of the cruciate ligament is called in a partial or complete tear of one or both cruciate ligaments. In extreme cases, it is a complete waste or avulsion, in which even parts of the bone can be affected. The bony avulsion or down is much less common than the pure ligament without ( intraligamentous rupture) bony involvement.