ACL Reconstruction

Facts

The Anterior Cruciate Ligament (ACL) is the most commonly injured ligament of the knee. The ligament is most commonly injured during an athletic activity. Due to the fact that sports are an increasingly important part of day to day life in the United States, the number of ACL injuries have steadily increased over the past few decades. This injury has received a great deal of attention from orthopedic surgeons over the past several years and the success of surgical reconstruction has greatly improved.

Biomechanics

The ACL controls how far forward the tibia moves in relation to the femur. If the tibia moves too far the ACL can rupture. The ACL is also the first ligament that becomes tight when the knee is straight. If the knee is forced past this point, or hyperextended, the ACL can also be torn. This tearing of the ligament results in a loud pop and the feeling of instability in the knee. The ACL may not be the only ligament injured when the knee is twisted violently, such as in a clipping injury in football. It is not uncommon to see both the medial collateral ligament (MCL) and the ACL injured as well as meniscus damage

Causes of injuries

The major cause of injury to the ACL is sports related. The types of sports which have been associated with ACL tears are numerous. Those sports requiring the foot to be planted and the body to change direction rapidly (such as basketball) carry a high incidence of injury. Football, of course, is frequently the source of an ACL tear. Football combines the activity of planting the foot and rapidly changing direction AND the threat of bodily contact. Downhill skiing is another frequent source of injury, especially since the introduction of ski boots that come higher up the calf. These boots move the forces caused by a fall to the knee rather than the ankle or lower leg. The ACL injury usually occurs when the knee is forcefully twisted, or hyperextended. Many patients recall hearing a loud pop when the ligament tears, and feel the knee give away.

Increasing numbers

There has been a dramatic increase in the number of females who suffer an ACL tear. This is in part due to the rise in women's athletics, but studies have shown that female athletes are more likely to suffer this injury when compared to their male counterparts. It is uncertain why this is the case. Initially, it was thought that females were at higher risk because of differences in training intensity. But more evidence suggests that there may be a difference in the anatomy of the female knee, or the female ligament may not be as strong due to the effects of the female hormone estrogen. These factors may lead to a higher risk of ACL injury for the female athlete.