What does the Anterior Cruciate Ligament look like?
From Wikipedia, the free encyclopedia
The anterior cruciate ligament (ACL) is a cruciate ligament which is one of the four major ligaments of the human knee. In the quadruped stifle (analogous to the knee), based on its anatomical position, it is referred to as the cranial cruciate ligament.[1]
The ACL originates from deep within the notch of the distal femur. Its proximal fibers fan out along the medial wall of the lateral femoral condyle. There are two bundles of the ACL—the anteromedial and the posterolateral, named according to where the bundles insert into the tibial plateau. The ACL attaches in front of the intercondyloid eminence of the tibia, being blended with the anterior horn of the lateral meniscus. These attachments allow it to resist anterior translation of the tibia, in relation to the femur.
Anterior cruciate ligament injury is the most common knee ligament injury, especially in athletes. Lateral rotational movements in sports like these are what cause the ACL to strain or tear. Strains can sometimes be fixed through physical therapy and muscle strengthening, though tears almost always require surgery. The most common method for repairing ACL injuries is arthroscopic surgery. Doctors will either use a patient’s own tendons, such as part of their hamstring, or ligaments from cadavers to construct a new ACL. Other common injuries accompanying ACL tears are meniscus, MCL, and knee cartilage tears.
A 2010 Los Angeles Times review[2] of two seemingly conflicting medical studies discussed whether ACL reconstruction was advisable. One study found that children under 14 who had ACL reconstruction fared better after early surgery than those who underwent a delayed surgery. For adults under 35, though, patients who underwent early surgery followed by rehab fared no better than those who had rehab therapy and later surgery.
The first report focused on children and the timing of an ACL reconstruction. ACL injuries in children, according to orthopedic surgeon Howard Luks, MD,[3] are a challenge because children have open growth plates in the bottom of the femur or thigh bone and on the top of the tibia or shin. An ACL reconstruction will typically cross the growth plates, posing a theoretical risk of injury to the growth plate, stunting leg growth or causing the leg to grow at an unusual angle. When children resume their usual activities, resulting instability episodes can cause tears of the medial or lateral meniscus or damage the articular cartilage on the ends of the bones. The study showed that ACL reconstruction within 12 weeks of injury was beneficial, minimizing the risk of associated injuries.
The second study noted in the L.A. Times piece[2] focused on adults and questioned whether an ACL reconstruction was necessary when an MRI-documented tear exists. But the indication for ACL reconstruction is not merely an existing tear; many patients without instability, buckling or giving way after a course of rehabilitation can be managed non-operatively. Patients involved in sports requiring significant cutting, pivoting, twisting, or rapid acceleration or deceleration may not be able to participate in these activities without ACL reconstruction and may want to consider an early reconstruction to minimize the risk of developing common associated injuries. “You can change your knee to suit your lifestyle,” says Dr. Howard Luks, “or change your lifestyle to suit your knee.”[3]
From Brown University
There are over 200,000 anterior cruciate ligaments (ACL) injuries that occur in the United States annually. (3) An anterior cruciate ligament injury is extreme stretching or tearing of the anterior cruciate ligament (ACL) in the knee. An anterior cruciate ligament (ACL) unravels like a braided rope when it’s torn and does not heal on its own. (8) This injury can be divided into the partial or complete tearing of the ACL ligament.
ACL tears may be due to contact or non-contact injuries. A blow to the side of the knee, such as may occur during a football tackle, may result in an ACL tear. Contrary to popular belief, coming to a quick stop, combined with a direction change while running, pivoting, landing from a jump, or overextending the knee joint, can also cause injury to the ACL. One study showed that contact resulted in 93% of injuries in the ground of 226 patients while non-contact sport resulted in the remaining 7%. For recreational athletes, the numbers were much more even. (6) Basketball, football, soccer, and skiing are the most common sports in which there are ACL tears.
The biomechanical function of the ACL is complex for it provides both mechanical stability and proprioceptive feedback to the knee. In its stabilizing role it has four (main) functions:
• Restrains anterior translation of the tibia
• Prevents hyperextension of the knee
• Acts as a secondary stabilizer to stress, reinforcing the medial collateral ligament
• Controls rotation of the tibia on the femur in femoral extensions of 0-30°. (7)
The ACL is widely known as the most important ligament in the knee. Therefore it is often treated with much more aggressive therapy, especially in competitive athletes. In most cases, the ACL is treated by various surgeries. (See Ligament Surgery for a description of the surgery) Sometimes, in the case of patients who are not very active, the ACL is not operated on. This is more common in elderly patients. In competitive athletes, the ACL is reconstructed surgically 90-100% of the time. In a 5 year study of ACL injuries in the National Football League, it was found that 31 out of 31 head physicians recommended operation for all of the ACL injuries that occurred. (4)
For the reconstruction surgeries, portions of the patellar tendon autograft account for most of the ACL surgeries performed in athletes. (2,5,4) Other sources of grafts for reconstruction include hamstring tendon autografts, semitendinosus, and gracilis tendon autografts, or Achilles tendon allografts. There are many other types of autografts, allografts, engrafts, and prosthetic ligaments which have been used in the population of patients, but the patellar tendon has been adopted as the gold standard for ACL reconstruction therapies for competitive athletes.
In most of the sports analyzed, ACL reconstruction surgery had a recovery time of between 6 and 9 months. After this time, most athletes had returned close to their full level of the previous play. Sources showed between 80% and 100% of the previous level. In most sports, it was found that around 90% of these athletes returned to play in their respective sports. After the first ACL injury, there is a risk of repeated injury. It is estimated to be between 5 and 15%. (5)
All in all, the tearing or sprain of the anterior cruciate ligament accounts for a large portion of knee injuries in sports. The standard surgeries and therapies currently in place provide good results and recovery time. A large proportion of athletes who have undergone ACL surgery return to their respective sport at a level close to their previous level of play.
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