The anterior cruciate ligament (ACL) is the most commonly injured knee ligament. It can tear when the knee is twisted or hyperextended, often during sports. ACL injuries have increased as sports have grown in popularity. While initial treatment focuses on reducing swelling and pain, many patients require reconstructive surgery followed by months of rehabilitation. Females are particularly at risk of ACL tears due to anatomical and hormonal factors. Prevention programs aim to strengthen muscles to reduce this risk.

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Alexis Cargle
Mrs. Corbett
Senior Project Research Paper
17 November 2011
ACL Injuries
The anterior cruciate ligament, more commonly known as ACL, is the most
common knee ligament injury. An ACL injury mainly affects athletes or those
participating in athletic activities. Over the years, sports have become more popular
which has led to an increase in anterior cruciate ligament injuries. This increase led
orthopedic surgeons to create many operations over the past fifteen years that reconstruct
this ligament.
The anterior cruciate ligament is located in the center of the knee joint where it
runs alongside the back of the femur and then connects to the front of the tibia. In the
article “A Patient’s Guide to Anterior Cruciate Ligament Injuries,” it says, “An ACL
injury usually occurs when the knee is forcefully twisted or hyperextended. Many
patients recall hearing a loud pop when the ligament is torn, and they feel the knee give
way” (Medical Multimedia Group, LLC, 4). The ACL is the main controller of how far
the tibia can move under the femur. If the tibia moves too far forward, it can cause the
ACL to rupture. When straightening the knee, the ACL is the first ligament to become
tight.
The major cause of an ACL injury is sports related. Sports that require the foot to
be planted and then the body to shift rapidly in direction carry a high risk for injury, such
as basketball, football, and downhill skiing. In the article “A Patient’s Guide to Anterior

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Cruciate Ligament Injuries,” it states “Usually, the knee joint swells within a short time
following the injury. This is due to bleeding into the knee joint from torn blood vessels in
the damaged ligament” (Medical Multimedia Group, LLC, 4). The knee can also feel as if
it is giving out whenever direction is being changed. It may feel like the knee is slipping
backwards. The swelling and pain from the injury last for two to four weeks, but the knee
can still feel unstable. The instability of the knee is what requires treatment. If the knee
remains unstable for a long time, it can lead to early arthritis.
Doctors diagnose an ACL injury based on treatment and history of the knee. In an
acute injury, swelling is a major indicator of a tear. If tense swelling occurs within hours
of the injury, it usually means blood is in the joint. If swelling occurs the next day, it is
most likely the inflammation which creates fluid to form in the joint. A doctor can place a
needle into the joint and drain the fluid; this reduces the swelling and relieves the pain.
This can be beneficial to the doctor because it gives important information on the knee. If
blood is found in the fluid, there is a seventy percent chance that it is torn. Another way
to diagnose an ACL injury is by an MRI, or magnetic resonance imaging. This requires
no needles and is painless.
Initial treatment is to reduce the swelling and pain. This is treated by rest and
medication such as Tylenol. Crutches can be used until walking without a limp is
obtained. Physical therapy is then done to help recovery. Therapists use ice, electrical
stimulation, and elevation to reduce the swelling. Range-of-motion exercises should be
done as soon as possible in order to gain back one hundred percent usage of the knee.
Stationary bikes, stretching gently, and application of pressure are included. An ACL
brace is suggested by the therapist and has to be custom made. The brace is to prevent

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further knee injury. However, it does not fully protect the knee while doing physical
activity or competing in sports. Wearing a brace a year after fixing the injury is also
advised.
Many types of surgeries can be done to reconstruct the ligament as well.
Medscape states that “Approximately 60,000-75,000 ACL reconstructions are performed
annually in the United States” (Gammons and Ho). A patellar tendon graft, a hamstring
graft, and allograft reconstruction are the types of grafting used. In a patellar tendon graft,
a tendon from the knee cap is stripped and used to replace the ACL. In a hamstring graft,
a tendon from one of the hamstrings that runs from the inside of the thigh and knee is
taken to replace the ACL. An allograft is tissue from another person. The allograft can be
from many different types of tendons. It takes less time because the tendon does not have
to be harvested from another location in the body.
Rehabilitation of the knee can take up to nine months. Rehabilitation is needed to
improve balance, reduce pain and swelling, restore range of motion, and regain strength.
In the article “Anterior Cruciate Ligament Inuries: Treatment and Rehabilitation,” it
states that the major goals of rehabilitation are “Restoration of joint anatomy, provision
of static and dynamic stability, maintenance of the aerobic conditioning and
psychological well being, and early return to work and sport”(Cross). It is important to
find the right balance in rehabilitating the knee. Being too aggressive can damage the
repair done by surgery and cause the ligament to tear again, but not doing enough can
make the healing process longer than necessary. More than eighty percent of patients

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who have surgery return to a normal lifestyle and only close to ten percent develop
permanent knee instability.
There are many ways to prevent ACL injuries. These ways include strengthening
the thigh muscles and maintaining a balance between the quadriceps and hamstrings.
Also, increasing flexibility and agility will reduce potential injury. In the article “Anterior
Cruciate Ligament (ACL) Injuries,” it states that people can “avoid wearing shoes with
cleats in contact sports, avoid wearing high-heeled shoes, and avoid sports that involve
lots of twisting and contact” (Anterior Cruciate Ligament) to prevent an ACL injury.
There are also prevention programs that can be attended. These programs include
plyometrics, balance, and strengthening and stability.
Lately, women’s sports have become more popular. In the article “ACL Injuries
in Female Athletes,” it reads “Over the last decade, torn and ruptured anterior cruciate
ligament (ACL) in female athletes have increased at an alarming rate” (Kaselj). It is
shown that women are two to four times more likely to injure the ACL than men in the
same sports. Women are not able to tighten the thigh muscle to the same degree as men
are. The knees are not able to hold as steady as they should which give less knee
protection during physical activity. The quadriceps and hamstrings in a woman work
differently than a man’s do. Women have to work harder than a man when bending the
knee. The tibia is pulled forward which puts the knee at risk for an ACL tear. The
hamstring muscles also respond slower than a man’s hamstrings. This may allow the tibia
to slide forward placing a strain on the anterior cruciate ligament. Many say that estrogen
can affect the weakness of the muscles as well.

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In basketball, women are five to seven times more likely to injury the anterior
cruciate ligament than a man playing basketball. Also, in 2009, female soccer players
were known to suffer more than twice the injuries as men while playing the game.
Between the ages of fifteen and twenty-five, women athletes are likely to suffer an ACL
injury. This is five years earlier than when a man initially injures his ACL. Anatomy
differences are one of the key factors of this. In the article “ACL Injuries in Female
Athletes,” it says “Women have lesser muscle strength and slower muscle reaction times
when compared to men. A strong and fast-reacting hamstrings is vital to keep the ACL
intact during abrupt changes of direction” (Kaselj). A woman’s pelvis is wider than a
man’s which causes a more tilted femur near the hips, and the shin is more angled to the
knee which places more strain on the ACL. The ACL comes through a notch, and women
have a narrower notch than men which weakens the ACL. The ACL itself is also smaller
in women which makes it more vulnerable. When women are on their menstrual cycle,
the chance for an ACL injury is higher because the hormonal levels are greater. Also,
women have weaker leg strength. These five factors create a greater risk of tearing the
anterior cruciate ligament.
An anterior cruciate ligament injury is a very common knee injury in athletes. The
growing popularity of women’s sports has led to an increase in ACL injuries. Females are
also more prone to this type of injury than a male is. Proper care can be done to prevent
an ACL injury and is suggested by doctors. Surgery is recommended for the best
reconstruction of the ligament, and rehabilitation is also key for the proper restoration.
With the right care and dedication to make these injuries better, restoring this ligament is
an easy process.

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Works Cited
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Injury in Skeletally Immature Athlete.” Sports Medicine July-Aug. 2008: 2-7.
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American Orthopaedic Society for Sports Medicine. “Anterior Cruciate Ligament (ACL)
Injury Prevention.” AOSSM Sports Tips. N.p., 2008. Web. 17 Oct. 2011.
<http://www.sportsmed.org/‌uploadedFiles/‌Content/‌Patient/‌Sports_Tips/‌ST
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Cross, Mervyn J. “ANTERIOR CRUCIATE LIGAMENT INJURIES: Treatment and
Rehabilitation .” Encyclopedia of Sports Medicine and Science. N.p., 1998. Web.
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Gammons, Matthew, MD, and Sherwin SW Ho, MD, eds. “Anterior Cruciate Ligament
Injury .” Medscape. N.p., 22 Sept. 2011. Web. 17 Oct. 2011.
<http://emedicine.medscape.com/‌article/‌89442-overview>.
Kaselj, Rick, MS. “ACL Injuries in Female Athletes.” Exercises For Injuries. N.p., 19
Aug. 2010. Web. 17 Oct. 2011. <http://exercisesforinjuries.com/‌acl-injuries-in-
female-athletes/>.

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Medical Multimedia Group, LLC. “A Patient’s Guide to Anterior Cruciate Ligament
Injuries.” eOrthopod.com. Orthopod, n.d. Web. 14 Oct. 2011. <http://www.soar-
physicaltherapy.com/‌pdfs/‌knee/‌Anterior_Cruciate_Ligament_Injuries.pdf>.
Rogers, Kenneth, PhD. “Anteiror Cruciate Ligament (ACL) Injuries.” Kids Health. N.p.,
June 2009. Web. 17 Oct. 2011.
<http://kidshealth.org/‌parent/‌medical/‌bones/‌acl_injuries.html#>.
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<http://www.txsportsmed.com/‌emedicineacl.php>.
Wedro, Benjamin, MD, and William C Shiel, Jr, MD, eds. “ACL injury (cont.).”
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