KNEE ANTERIOR CRUCIATE LIGAMENT ANATOMY
Knee Anterior Cruciate Ligament Anatomy models 3D knee

The anterior cruciate ligament runs upwards and backwards from its tibial origin near the front of the tibial plateau, to its attachment at the posterolateral part of the intercondylar notch of the femur. The anterior cruciate ligament prevents forward movement of the tibia in relation to the femur, and with the posterior cruciate ligament, stabilizes the knee in the anteroposterior direction and allows the joint to work as a hinge while keeping the articular surfaces in contact. Knee Anterior Cruciate Ligament Anatomy models 3D knee.

The two cruciate ligaments, along with other ligaments and muscles, cause the rolling – sliding movements of knee flexion and extension. The anterior cruciate ligament consists of closely attached ligament bundles, which spiral around each other ninety degrees. They are each taut and supportive during different knee positions. Knee Anterior Cruciate Ligament Anatomy models 3D knee.

The cruciate ligaments lie in the centre of the joint, largely within the intercondylar notch.

The anterior cruciate ligament is attached to the anterior intercondylar fossa of the tibia, along the edge of the medial condyle and between the insertion of the anterior horn of the medial meniscus anteriorly and that of the lateral meniscus posteriorly. It runs obliquely superiorly and laterally and is attached above to a narrow patch on the internal aspect of the lateral condyle of the femur which extends vertically above and along the edge of the articular cartilage. The ligament has a more anterior attachment to the tibia and a more lateral attachment to the femur than its fellow. Knee Anterior Cruciate Ligament Anatomy models 3D knee

Behind the anterior cruciate ligament is the posterior cruciate ligament. It is attached to the posterior part of the posterior intercondylar fossa of the tibia, overlapping the posterior rim of the upper surface of the tibia. Its tibial insertionis placed well posterior to the insertion of the posterior horns of the lateral and medial menisci. The ligament runs obliquely medially, anteriorly and superiorly to be inserted into the depths of the intercondylar notch and also to a patch on the edge of the lateral surface of the medial condyle along the line of the articular cartilage. This ligament has a more posterior attachment to the tibia and a more medial attachment to the femur than its fellow. Knee Anterior Cruciate Ligament Anatomy models 3D knee.

The posterior cruciate ligament is constantly accompanied by the menisco-femoral ligament, which is attached below to the posterior horn of the lateral meniscus. The menisco-femoral ligament clings to the anterior surface of the posterior cruciate ligament and runs with it to a common insertion into the lateral surface of the medial condyle. Occasionally a similar ligament is present in relation to the medial meniscus, where a few fibres of the anterior cruciate ligament are inserted into the anterior horn of the medial meniscus near the insertion of the transverse ligament. Knee Anterior Cruciate Ligament Anatomy models 3D knee.

The cruciate ligaments touch each other on their axial borders with the anterior running lateral to the posterior ligament.They do not lie free within the knee joint cavity, but are lined by synovium. The cruciates are so intimately related to the capsule that they can be considered as thickenings of the capsule. The joint capsule dips into the intercondylar notch to form a double-layered partition along the axis of the joint. The capsular attachment passes through the attachments of the cruciates and the thickenings of the capsule, formed by the cruciates, stand out on the capsule's external surface. Knee Anterior Cruciate Ligament Anatomy models 3D knee.

The fibres of the cruciates have different lengths and direction, so that during knee movements, they are not all stretched at the same time. The anterior cruciate ligament posses very little inherent elasticity. Application of a force straining it by more than 5% of its resting length will result in rupture. This rupture may be complete and obvious on gross inspection, or it may be partial, demonstrating failure in continuities. The anterior cruciate ligament is able to resist force of 1700N before failure.

In the middle of the knee joint, the capsular partition, thickened by the cruciate ligaments, divides the cavity into a lateral and a medial compartment. This partition is extended anteriorly by the infrapatellar fat pad. Each compartment is in turn divided into two storeys by the meniscus. The upper or suprameniscal storey corresponding to the line of contact between femur and meniscus, and the lower of inframeniscal storey corresponding to the line of contact between the tibia and the meniscus. Knee Anterior Cruciate Ligament Anatomy models 3D knee.

In the sagittal plane, the cruciate ligaments are crossed, with the anterior cruciate ligament running obliquely superiorly and posteriorly, and the posterior cruciate ligament running superiorly and anteriorly. They are also crossed in the frontal plane as their tibial attachments lie on the anteroposterior axis of the joint, while their femoral insertions are 1.7 cm apart. Thus the posterior cruciate ligament runs obliquely superiorly and medially, and the anterior cruciate ligament obliquely superiorly and laterally. In the horizontal plane, they run parallel to each other and are in contact at their axial borders. Knee Anterior Cruciate Ligament Anatomy models 3D knee.

The cruciate ligaments not only cross each other in space, but also th eipsilateral collateral ligament. So the anterior cruciate ligament and the lateral collateral ligament are crossed, and the posterior cruciate ligament and the medial collateral ligament are also crossed.

The cruciate ligaments do not have the same angle of inclination. Thus in full extension, the anterior cruciate ligament is more vertical while the posterior cruciate ligament is more horizontal. Their femoral insertions show a similar difference: the insertion of posterior cruciate ligament is horizontal, while that of the anterior cruciate is vertical.

The cruciates also exhibit a constant length ratio. In every individual. the posterior cruciate ligament is shorter, being equal to three-fifths of the anterior cruciate. This ratio is one of the essential features of the knee, and it determines at once the mechanism of action of the cruciates and the shape of the femoral condyles. In the adult, the tibial insertions are about 5 cm apart.

The cruciates stabilise the knee in the antero-posterior direction and allow the joint to work as a hinge while keeping the articular surfaces in contact. Starting from the extended position, flexion causes the femoral surface to be tilted and the posterior cruciate to rear itself up, while the point of crossing of the ligaments slidesposteriorly and the anterior cruciate comes to lie horizontally. By lying flat on the tibia, the anterior cruciate ligament cleaves th eintercondylar eminence like a bread-knife. During flexion it comes to rest between the two tibial tubercles. When the knee is flexed to ninety degrees, the anterior cruciate is completely horizontal while the posterior cruciate becomes vertical. In full flexion, the anterior cruciate is slackened. During hyperextension, both cruciates are stretched. The anterior cruciate supports the vault of the intercondylar notch. As the cruciates consist of fibres of unequal length, there are always parts of the ligaments that are under tension. Also, the shape of the condyles is geometrically determined by the length of the cruciates, their length ration and the arrangement of their insertions. Knee Anterior Cruciate Ligament Anatomy models 3D knee.

The movement of the femoral condyles on the tibial condyles combines rolling and sliding. The extensor muscles pull the tibia forward under the femur during extension, and conversely the flexors draw the tibial plateau posteriorly during flexion. However it is the cruciate ligaments that pull back on the femoral condyles and make them passively slide on the tibial plateau in a direction opposite to their rolling movement. From the position of extension, During flexion, the anterior cruciate pulls back the condyle anteriorly, and is responsible for the sliding movement of the condyle anteriorly while the condyle rolls posteriorly. During extension, the posterior cruciate is responsible for the sliding movement of the condyle posteriorly while the condyle rolls anteriorly. Knee Anterior Cruciate Ligament Anatomy models 3D knee.

Axial rotation of the knee can only occur when the knee is flexed. In full extension, axial rotation is impossible, being prevented by the tension of the collateral and cruciate ligaments. When seen from above, the cruciate ligaments run obliquely, the anterior cruciate inferiorly, anteriorly and medially, the posterior cruciate inferiorly, posteriorly and laterally. They are coiled anticlockwise round the axis of rotation in the right knee. If the tibia rotates laterally under the femur,the cruciates become separated and vertical, and the tibia moves away slightly from the femur. Therefore lateral rotation relaxes the cruciates. Conversely, if the tibia rotates medially, the cruciates come into contact along their axial borders and become coiled round each other so that they are effectively shortened and the tibia is pressed against the femur. Therefore medial rotation tightens the cruciates. As the femoral condyles are already in contact with the tibial condyles, it is easy to understand why the cruciates prevent medial rotation when the knee is extended. Knee Anterior Cruciate Ligament Anatomy models 3D knee.

A similar line of reasoning can be developed to explain the role of the collateral ligaments. These run obliquely and they are coiled clockwise in the right knee, around the axis of rotation. If the tibia is medially rotated, the collateral ligaments become more vertical and the tibia moves away from the femur. ie medial rotation relaxes the collateral ligaments. If the tibia is laterally rotated, the collateral ligaments become more oblique, and the tibia is pressed more strongly against the femur ie lateral rotation tightens the collateral ligaments, so the collateral ligaments prevent lateral rotation of the knee in extension. Hence the rotational stability of the knee is secured by the collateral and cruciate ligaments.

Knee Anterior Cruciate Ligament Anatomy models 3D knee. This information is taken from I.A. Kapandji's The Physiology of the Joints Volume Two The Lower Limb, D.C. Reid's Sports Injury Assessment and Rehabilitation, and the Oxford Textbook of Sports Medicine.

Loading more stuff…

Hmm…it looks like things are taking a while to load. Try again?

Loading videos…