What is the cruciate ligament?
The cruciate ligament (Ligamentum cruciatum) is one of several ligaments that guarantee the stability of the knee joint. Strictly speaking, each knee has two cruciate ligaments: an anterior cruciate ligament (Ligamentum cruciatum anterius) and a posterior cruciate ligament (Ligamentum cruciatum posterius). The two ligaments consist of collagenous fiber bundles (connective tissue) and connect the thigh (femur) and shin (tibia). They sit centrally between the articular surfaces of the two leg bones and cross each other, as the name suggests. The anterior cruciate ligaments each pull from the outside of the back to the inside of the front, while the posterior ones pull in opposite directions.
Posterior cruciate ligament
The posterior cruciate ligament, which consists of two bundles, is thicker than the anterior and is the strongest of all the ligaments of the knee joint. It tears at around 80 kilograms. Intraarticularly, it reaches a length of about three to four centimeters and a width of about 13 millimeters.
Anterior cruciate ligament
The anterior cruciate ligament is composed of three collagen bundles that are twisted against each other, similar to strands of a rope. Compared to the posterior cruciate ligament, it is longer and has a poorer blood supply. It can withstand a load of around 40 kilograms.
What is the function of the cruciate ligament?
Due to their oblique position, the cruciate ligaments – both anterior and posterior cruciate ligaments – are always tense, regardless of whether we extend or bend the knee. During external rotation, the cruciate ligaments rotate apart; during inward rotation, they prevent too much inward rotation by wrapping around each other.
Where is the cruciate ligament located?
The cruciate ligaments are among the central or internal ligaments of the knee. They are located in the joint (intraarticular) between the articular surfaces of the femur and tibia, but attach outside the joint capsule (extracapsular) to the femur and tibia. Surrounding the cruciate ligaments are the menisci. The blood supply to the cruciate ligaments is provided by the genus media artery, which travels down the back of the leg to the knee joint.
What problems can the cruciate ligament cause?
As with any ligament, the cruciate ligament can be strained, sprained, overstretched and ultimately torn.
The first indication of a cruciate ligament tear is given by the so-called drawer phenomenon (hyperextension test). If the lower leg can be pulled forward one to two centimeters like a drawer in the flexed position, the anterior cruciate ligament is torn. If it moves backwards, the posterior cruciate ligament is affected. This becomes especially clear if the function of the collateral ligaments is also impaired.
Due to poor blood circulation, injuries to the anterior cruciate ligaments hardly heal on their own and therefore usually require surgery. The posterior cruciate ligaments are mainly affected by falls and accidents involving fractures of the upper or lower leg (femur fracture, tibial plateau fracture). Because the posterior cruciate ligament has a better blood supply, it is more likely to heal spontaneously.
