The anterior cruciate ligament (ACL) is located in the middle of the knee (it is part of the "central pivot"). Placed in the indentation of the femur, a real cavity in the middle of the knee, it is oblique upwards, backward, and outwards.
The knee joint is the largest of all. It is divided into three joints:
- the intermediate patellofemoral joint, between the patella and the patellar surface of the femur (thigh bone);
- the external femoral-tibial joint, between the external femoral condyle, the external meniscus, and the external tuberosity of the tibia (leg bone);
- the medial femoral-tibial joint, between the medial femoral condyle, the medial meniscus, and the medial tuberosity of the tibia.
The patellofemoral joint is flat, while the two femorotibial joints are hinged.
Among the various anatomical structures that make up the knee joint are the two cruciate ligaments, which intersect symmetrically in the center of the knee:
- the anterior cruciate ligament begins at the front end of the tibia, crosses the knee joint diagonally backward, and then attaches to the posterior part of the lateral femoral condyle;
- The posterior cruciate ligament extends from the rear end of the tibia to cross forward and inward to the anterior part of the medial femoral condyle.
This crossing is accentuated in particular during flexion and extension movements of the knee, or during rotation movements of the leg.
1. What is the purpose of the anterior cruciate ligament?
The two cruciate ligaments are essential for stabilizing the knee. The anterior cruciate ligament controls changes in direction such as rotation and twisting movements. The role of the anterior cruciate ligament is essential: it prevents the tibia from moving too much in relation to the femur and it also prevents excessive rotation of the tibia in relation to the femur.
In approximately 70% of serious knee injuries, the anterior cruciate ligament is stretched or torn.
2. What are the pathologies related to the anterior cruciate ligament?
The main damage to the anterior cruciate ligament is ligament rupture.
The rupture of the anterior cruciate ligament of the knee refers to a retraction of this ligament at both ends. This tear, partial or total, is most often of traumatic origin. It is quite frequent in sportsmen, the main sports at risk being soccer, skiing or even combat sports. These sports put a lot of strain on the knee, with rotational movements that are more likely to cause a ligament tear. The trauma can be direct, with a blow to the knee, for example, or indirect if it is a twisting movement leading to a sudden rupture of the ligament (the foot is blocked on the ground, but the knee pivots).
Thus, the most effective means of prevention to reduce the risk of tearing is muscle strengthening and warming up before physical effort. These conditions will make the knee more resistant during jumps or pivots.
The first symptoms of an ACL rupture appear immediately after the trauma. The main symptoms are severe pain in the knee, local swelling, cracking, a feeling of instability and fragility, as well as problems with the function of the knee (difficulty in stretching the knee, walking, etc.).
Subsequently, the rupture of the anterior cruciate ligament results in instability of the knee and a feeling of discomfort in everyday life. Certain knee movements, such as twisting and turning, are difficult, which can be disabling and affect quality of life. Similarly, when the ligament is damaged, the patient is hampered in his or her sports activities, especially in any activity requiring specific movements such as pivots.
3. What are the treatments?
The rupture of the anterior cruciate ligament cannot heal naturally and may require knee surgery.
The operation, called ligamentoplasty, consists in replacing the ruptured ligament. The principle is therefore a reconstruction of the ligament by autograft (harvesting from the patient himself).
This operation is performed under local or general anesthesia. It is performed under arthroscopy, i.e. with the help of an arthroscope introduced into the joint with a small camera. This makes it possible to visualize the lesions and to operate without opening the knee joint.
Several small instruments are then introduced to perform the surgical procedure.
To replace the ruptured ligament, several types of transplants can be used (patellar tendon, hamstring tendons, etc.).
A short incision is made to remove part of the tendon in question, which will be placed in the knee to replace the ruptured ligament.
The consequences on the tendon from which a part has been removed are minimal, if any because it will heal well and should hardly lose any function.
Post-operative rehabilitation can be done with the help of a physiotherapist or in a rehabilitation center. The goal is to reduce pain, maintain flexibility and mobility of the joint in the first instance, and then recover the muscles in the second instance.
The patient will also wear a splint for several weeks to help support the joint, as well as canes or crutches to relieve the weight of the knee.
Recovery of mobility and muscle strength takes place within a few months. However, a new rupture can always occur in the replacement ligament. Therefore, the state of the muscles is a major element to consider before pushing the knee to its limit, especially in sports. The patient must remain vigilant in his or her sports activities and, in particular, in any sport where the knee tends to rotate.
The results of this technique are nevertheless generally satisfactory. It also allows for the preservation of the rest of the knee structure (meniscus, cartilage, etc.) which degrades less significantly on a stable knee.
4. Who are the anterior cruciate ligament specialists?
Doctors specializing in anterior cruciate ligaments are orthopedic surgeons.
In case of pathology related to the anterior cruciate ligament, the attending physician will refer the patient to a specialist, who will determine the severity of the pathology and suggest or not medical-surgical management.
5. What are the diagnostic and complementary examinations?
The clinical diagnosis to confirm or not the rupture of the anterior cruciate ligament is made by an orthopedist.
The clinical examination of an ACL rupture consists first of an interrogation of the patient to determine the circumstances of the occurrence and to evaluate the symptoms felt. In most cases, at the very moment of the trauma causing the rupture, it is possible to hear a cracking sound in the knee. The patient usually experiences severe knee pain and swelling almost immediately. This is compounded by the instability of the knee, making it extremely difficult and painful for the patient to walk, who may feel as though they are walking into a hole or losing control of their knee. In some of the more severe cases, bleeding may occur as well as a total locking of the knee due to trapped tissue.
However, in some cases of partial rupture, the characteristic cracking sound may not be heard and the patient may still be able to walk.
To confirm the diagnosis, the orthopedic physician then performs tests such as the Lachmann maneuver (or anterior drawer maneuver). The goal is to look for abnormal slippage of the tibia in relation to the femur. To do this, the doctor positions the patient's knee between 0 and 30° in order to put tension on the anterior cruciate ligament bundles. In the case of a healthy ligament, the maneuver is characterized by an early hard stop of the tibia. In contrast, in the case of a rupture of the anterior cruciate ligament, the maneuver is characterized by a less clear-cut and delayed arrest. The reaction of the knee can be compared to the other knee if it is healthy, to confirm damage to the anterior cruciate ligament. In addition, the doctor can look for other possible injuries on clinical examination, such as damage to the menisci or collateral ligaments.
However, due to the swelling and severe pain associated with this method, it is difficult to perform and interpret immediately after the ligament rupture.
When the clinical examination is not conclusive, additional radiological examinations are necessary to characterize the pathology.
An X-ray may or may not reveal the presence of a fracture following the trauma. MRI (magnetic resonance imaging) allows for a very precise diagnosis and observation of the inside of the knee, but it does not allow for the evaluation of the functionality of the remaining ligament, which only a clinical examination can reveal. Therefore, there is no urgency to perform an MRI, which can be performed 1 month after the rupture, except in rare cases. Here again, it is the performance of a good clinical examination that will indicate the need to perform an emergency MRI.
If MRI is not indicated, the doctor may use a more invasive arthroscanner. For this, a product is injected directly into the knee joint to allow visualization of the various tissues. Combined with standard X-rays, these imaging examinations can also identify other lesions such as meniscus damage.
Sources :
Définition rupture ligaments croisés - symptomatologie
Principes d’anatomie et de physiologie (livre J Tortora et NP Anagnostakos)
No comments:
Post a Comment