The Anterior Cruciate Ligament, commonly referred to as the ACL, is a dense band of tissue that provides stability to the knee. Fibers of the ACL can be injured or torn when abnormal movement forces the ligament beyond its capacity. Typically, a combination of motions involving twisting at the knee while weight-bearing results in excessive load and rupture of the ACL.
ACL injuries are often in non-contact environments, meaning the player was not necessarily in a collision or contact with another payer, but rather cutting, changing directions, or landing from a jump. These injuries are devastating for an athlete and often bring the season to an abrupt halt in order for proper rehabilitation (likely including surgery) to take place.
Many victims of torn ACLs have certain characteristics in common and identify with several of the risk factors which may predispose them to a non-contact ACL injury. While some risk factors are modifiable and others are not, understanding and addressing such factors with proper training and good decision-making can ultimately reduce the likelihood of sustaining such a severe knee injury.
Anatomical and structural characteristics, neuromuscular control issues, and extrinsic variables have been identified as factors contributing to increased risk for suffering from an ACL injury.
Certain anatomical and structural characteristics place the ACL in a more vulnerable position for maintaining stability of the knee. Variations in the anatomical development of the knee, such as the depth of the intercondylar notch and the thickness of the ACL tissue, have been shown to be associated with tears and ruptures. Increased joint angles and body alignment through the pelvis, hip, and knee may naturally predispose one to be at higher risk as well.
Females have a 9 times greater rate of non-contact ACL ruptures for various reasons related to strength, structure, hormones, and biomechanics – a topic that will be covered in more detail in another article (and deserves an article of its own). Many individuals demonstrate general ligament laxity, having a natural tendency to hyperextend their knees, elbows, or thumbs. Ligament laxity, or joint hypermobility, has been correlated with a higher risk of ACL injury. Additionally, having a prior history of ACL injury also places an individual at higher risk for re-injury.
While the anatomical and structural risk factors mentioned above are generally non-modifiable, they are valuable in understanding one’s risk. The more factors that an athlete identifies with, the greater the overall risk. For example, a female with “knock-knees”, general ligament laxity, lack of body control (described below), and a prior history of ACL injury has a greater likelihood of sustaining another non-contact ACL injury compared to someone without these identifiable risk factors.