The cruciate ligaments are among the most important supporting ligamentous apparatus in the knee joint. Along with the inner ligament and the outer ligament, the cruciate ligaments provide stability in the joint. When the cruciate ligament is injured (cruciate ligament tear), joint stability is severely limited or no longer present.
What is the cruciate ligament?
Schematic diagram of healthy cruciate ligaments and the different forms of cruciate ligament tears. Click to enlarge. The ligamenta cruciata genus – the cruciate ligaments – are part of the main apparatus of the knee joint. In addition to the inner ligament – the ligamentum collaterale tibiale – and the outer ligament – the ligamentum collaterale fibulare – the anterior and posterior cruciate ligaments provide stability to the joint. The cruciate ligaments, as the name suggests, cross at the center of the knee joint. The main task is to maintain stability during joint movement.
Anatomy and structure
The anterior cruciate ligament is located between the tibia with the femur. The anterior cruciate ligament runs from the front downward, or inward. Thus, the direction of the anterior cruciate ligament is opposite to that of the posterior cruciate ligament. The anterior cruciate ligament is supplied arterially via the genus media artery. The distribution of blood vessels in the anterior cruciate ligament is not homogeneous. However, the center of the cruciate ligament is free of blood vessels. The posterior cruciate ligament also runs between the femur and the tibia. However, the posterior cruciate ligament runs from the front to the top, or inward, and from the back to the bottom, or outward. Thus, the direction of the posterior cruciate ligament is opposite to the anterior cruciate ligament.
Function and tasks
The anterior and posterior cruciate ligaments are responsible for stabilization in the knee joint. Doctors believe that the cruciate ligaments are among the most important factors responsible for a stable knee joint. The ligaments cross each other in the middle of their course, which is why they have been given the name “cruciate ligament”. The greatest load is on the anterior cruciate ligament. It is also one of the most stressed ligaments in the knee joint and is largely responsible for keeping the joint stable during movement. The anterior cruciate ligament is also responsible for limiting the rotation of the knee joint. The posterior cruciate ligament is responsible for stabilizing the knee joint, with the other ligaments, during movement. The posterior cruciate ligament also ensures, in interaction with the other ligaments in the knee joint, that the rotation of the joint is restricted.
Diseases and complaints
If the knee is hyperextended or forcibly bent, when the thigh muscle is tensed, the anterior cruciate ligament tears. With the tear of the anterior cruciate ligament, other injuries to the knee joint are possible. Complex injuries often occur, such as damage to the medial meniscus as well as an injury to the medial ligament. The medical profession then speaks of an “unhappy triad” when all three factors (medial meniscus, medial ligament and anterior cruciate ligament) are injured. If the anterior cruciate ligament is torn, the patient complains of a severely swelling bruise in the knee joint. The knee can be pushed forward (the drawer effect), with a feeling of instability (giving way). Furthermore, the patient complains of pain as well as limitations in mobility. As a rule, the injured cruciate ligament is not sutured; rather, it is surgically replaced. This surgical method leads to the best long-term results. In anterior cruciate ligament reconstruction, a tendon is taken from between the tibia and the kneecap and formed into a new anterior cruciate ligament. The posterior cruciate ligament can also tear. Again, only if there is direct force on the knee joint, in a flexed state. Overextension can also sometimes be responsible for tearing the posterior cruciate ligament. Statistically, however, the posterior cruciate ligament tears less frequently than the anterior cruciate ligament. When the posterior cruciate ligament is torn, the knee joint swells and causes pain to the patient. Many patients also complain of joint effusion. In contrast to a tear of the anterior cruciate ligament, a posterior displacement of the knee joint occurs. The person is further limited in his mobility. A stretching of the knee joint is no longer possible. However, a complex injury rarely if ever occurs. In the case of a tear of the posterior cruciate ligament, surgery is rarely performed. As a rule, this is only performed on athletically active and young persons.Here, too, the cruciate ligament is replaced by a tendon of the kneecap. However, surgery is rarely used because with proper treatment and splinting, the posterior cruciate ligament heals itself. Strains or gentle tears in the cruciate ligament are also possible and are considered long-lasting injuries. Injury to the cruciate ligament (especially the anterior ligament), are serious injuries and can sometimes cause long-term damage (the patient can no longer bend or extend the knee 100%); therefore, after surgery, long physical therapies are inevitable and necessary.
