What is the cruciate ligament? The cruciate ligament is an important structure within the knee joint and performs an important function. The cruciate ligament is located inside the knee joint and is divided into two anterior and posterior branches, depending on where it attaches to the tibia. The cruciate ligament occupies the intercondylar space and is also known as the “cruciate ligament” because the two anterior and posterior branches cross like a cross. What does the cruciate ligament do? The cruciate ligament of the knee has a very important function in keeping the femur (thigh bone) and tibia (lower leg bone) stable. During knee flexion, the posterior cruciate ligament prevents the tibia from shifting backward over the femur, preventing excessive extension and flexion. The anterior cruciate ligament prevents the tibia from shifting forward on the femur, i.e., the femur shifts backward, and prevents excessive knee extension. It prevents internal rotation of the femur when the leg is immobilized. In conclusion the cruciate ligament of the knee is an important function in maintaining the stability of the knee joint, so it must be reconstructed after injury. What are the causes of cruciate ligament injuries? Because the posterior cruciate ligament is thicker than the anterior cruciate ligament, there is less chance of injury than the anterior cruciate ligament. Common causes of ACL injuries are antagonistic sports (sports injuries), most commonly in basketball, soccer, volleyball and skating, and to a lesser extent in traffic injuries and falls. ACL injuries generally occur when the lower leg is immobilized while the thigh and upper body are extremely twisted. What are the signs of an ACL rupture? In acute injuries such as strong knee hyperextension or hyperextension injuries, the patient feels a tearing sound in the knee joint, followed by weakness of the knee joint, severe joint pain, rapid swelling, and limitation of joint flexion and extension. In some cases, subcutaneous petechiae are seen around the joint. Symptoms vary depending on the type of rupture: severe pain in partial ruptures and mild pain in total ruptures. In a total rupture with old injury, the patient has a sensation of weakness in the knee when walking, the affected limb tends to kneel when jumping up and down, and the thigh muscles (quadriceps) atrophy. MRI can provide the basis for a definitive diagnosis, and knee arthroscopy Knee arthroscopy has both a diagnostic role and allows for minimally invasive surgery to reconstruct the ruptured cruciate ligament. Depending on the degree of rupture, there are complete and partial ruptures. What are the signs of a posterior cruciate ligament rupture? When the affected knee is injured, tearing sounds can often be heard, or a tearing sensation falls to the ground, with severe pain and rapid swelling of the knee. Initially, the swelling is confined to the joint, but when the posterior joint capsule ruptures, the swelling spreads to the N-fossa and involves the posterior aspect of the calf, with gradual subcutaneous bruising, indicating leakage of intra-articular bleeding into the posterior knee and the gastrocnemius and hallux valgus spaces. If the knee is combined with MCL or LCL injury, abnormal motion of internal and external rotation and internal and external rotational instability may occur, with localized pain and swelling of the ligament and a positive Jerk test. a positive Jerk test indicates anterolateral rotational instability of the knee, demonstrating injury to the MCL (including the MCL and medial capsular ligament) of the knee. The test is often performed after the acute phase has passed. The method is to have the patient lie supine with the hip flexed at 45° and the knee flexed at 90°, while internally rotating the tibia and applying valgus stress to the upper calf, then gradually straightening the knee to a 20° to 30° position, the lateral femoral and tibial articular surfaces may become subluxed. A positive result is obtained when the knee joint is further straightened and a popping sensation and ringing occurs as a result of natural repositioning. Another method is: extend the knee position, rotate the lower leg externally or neutrally, try external rotation stress on the knee joint and gradually flex it to 20° to 30° position when there is a popping sound and dislocation feeling is positive. Drawer test The drawer test is positive after checking after 90° of knee flexion. However, due to the severe pain and muscle spasm caused by flexion of the knee, the posterior drawer test is often difficult to perform, and in some cases a negative result leads to misdiagnosis. The posterior drop sign of the flexed knee calf can be examined as shown. The patient is made to lie flat on his back with the knee extended and completely relaxed, and for PCL fracture, the examiner slowly lifts the lower thigh of the affected side 10 cm above the knee with both hands, and the upper tibial segment is seen to slide backward. The inferior patellar segment was clearly collapsed. For ACL rupture, the examiner slowly lifts the upper part of the affected calf with both hands 10 cm below the knee, and the lower femoral segment is seen to slide backward and the superior patellar segment collapses. Each case should be examined by elevating the upper and lower knee once, and bilateral comparison can determine whether there is an anterior or PCL injury. The step sign is positive if the medial tibial plateau is smaller or disappears when the thumb is slid downward from the medial femoral condyle at 90° of knee flexion, indicating PCL injury. Whole blood can be obtained by arthrocentesis, and intra-articular fracture is indicated if there are oil beads in the blood. Tibial external rotation test (dial test) To check for posterior lateral instability of the injured knee, the external rotation of the tibia on the femur can be measured at 30° and 90° of knee flexion. This can be done in the supine or prone position. An increase in external rotation of >10° with pain compared to the contralateral side at 30° of knee flexion, but not at 90°, is indicative of a simple posterior external angle injury. An increase in external rotation of >10° at both 30° and 90° of knee flexion suggests injury to both the PCL and posterior lateral horn. How are cruciate ligament injuries treated? With increased awareness of the importance of the function of the cruciate ligament, an injury can cause severe instability in the knee joint, affecting daily life and sports. Incomplete ruptures can be treated conservatively by wearing a brace, and those with laxity can undergo arthroscopic reduction surgery. A complete rupture of the cruciate ligament must be reconstructed to restore stability to the knee joint. Because of the short length of the cruciate ligament, it is difficult to heal with direct sutures after a complete rupture, so direct sutures have now been abandoned in favor of reconstructive surgery. Due to the development of arthroscopic techniques, surgical treatment of both cruciate ligament and meniscal injuries is now performed arthroscopically, with the advantage of a minimally invasive recovery. There are three main types of tissues used to reconstruct the cruciate ligament: one is homogeneous allogeneic tendons (taken from fresh cadavers and commercialized after special treatment), including allogeneic patellar ligament (B-T-B), Achilles tendon and anterior tibial tendon; one is autologous tendon tissues, including autologous patellar ligament, quadriceps muscle and N cord tendon (semitendinosus and thin femoral tendon); and the other is artificial ligament.