(Refer to picture on the right)
An ACL, Anterior Cruciate Ligament, is one of the two ligaments (ligaments connect bone to bone) located inside the knee. Both the Femur (bone above the knee) and Tibia (Bone below the knee - shinbone) hold the ACL together, and vice versa. The 2 cruciate ligaments being the ACL and PCL, posterior cruciate ligament, cross inside your knee like an “X”. Since the ACL is anterior, that means it lies in front of the PCL. The ACL connects to the medial meniscus and to the lateral aspect base of the femur.
The ACL has several functions: protection, movement, and stability. Its attachments (femur and tibia) hold the ACL together and helps the leg flex or bend in order to walk. The ACL protects the shin bone from sliding forward, as well as provides rotational stability for the knee. Stability is important especially to athletes who participate in activities involving vigorous cutting (changing direction), jumping, and rapid deceleration. Lack of stability or protection to the ACL can cause injury to the ligament.
The ACL can tear in several ways, through contact or non-contact (most common):
ACL tears are more common in females because of differences in anatomy (pelvis width and ACL size) , hormones, bio mechanics, (landing position and knee angle/knock-kneed).
Injured ligaments are considered "sprains" and are graded on a severity scale. Partial tears are rare; most ACL injuries are complete or almost completely torn.
The ligament is mildly damaged and has been slightly stretched, but is still able to help keep the knee joint stable. This minor trauma or "sprain" to ligament causes some ligament fibers are stretched but none are torn.
The ligament is stretched to the point where it becomes loose. This is a “partial tear” of the ligament and some fibers are actually torn.
This type of sprain is a “complete tear” of the ligament it's the most severe ACL knee injury. The ligament has been split into two pieces, and the knee joint is unstable. Severe trauma to the ligament, which completely tears all the ligaments fibers.
Extrinsic Risk Factors
Outside (external) factors that contribute to tearing an ACL. People wearing shoes with longer, irregular cleats have an increased risk of ACL injury, because of increased friction at the foot-to-turf interface. Dry weather increases the risk of ACL injuries on natural grass
Intrinsic Risk Factors
Inherited (Internal) factors that contribute to tearing an ACL.
The ACL has receptors for estrogen, testosterone, and relaxin, which means that sex hormones may affect the mechanical properties of the ACL and influence the risk of ACL injury. Female’s ACL have half a millimeter more laxity during their menstrual cycle. Sex hormones influence ACL injury risk through indirect effects on neuromuscular growth and maturation during puberty. These influences can ultimately lead to an ACL tear. During puberty, male’s undergo large testosterone surge, which increases their muscle mass and strength, allowing them to better control their body during athletics. Females don’t experience large testosterone surges, only a small increase in testosterone levels. This results in a much smaller increase in muscle mass and strength, which may not be enough to control their body during athletics.
Females are more prone to ACL tears because they use their muscles differently than males, when landing from a jump or quickly changing direction. Females also tend to have one leg stronger than the other.
Females tend to use their quadriceps (thigh muscles) much more than their hamstring muscles. Females also tend to have reduced knee flexion, or don’t bend their knees as much as males do when jump landing or quickly changing directions. Reduced knee flexión increases quadriceps activity, and decreased hamstring activity compared with male. When the quadriceps are used more than the hamstrings, this causes the knees to turn inwards leading to an ACL tear.
An ACL tear is an acute injury (happens at an instant), when an ACL is torn people encounter:
Refer to a physician
Balance training: balance exercises
Learn more about how to prevent an ACL tear through videos. Step by step instructions on how to properly perform exercises are provided.
The most commonly recommended autograf in young athletes. A piece of your patella (knee cap) is removed, as well as the patellar tendon, and a also piece of your tibia (shinbone.)
The hamstring allows the knee to bend and straighten the hip. Most commonly used for growing children and adolescents.
Using a donor graft, usually a cadaver’s Achilles tendon, (muscle on the back of the heel).
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