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The volleyball match has been going on for over an hour. Both teams
have been trading points and side-outs. The ball is set high outside so
that the big outside hitter can put the ball away. She comes in hard,
plants, leaps into the air and smashes the ball down the line in a
twisting motion. As she lands on her right leg, a POP is heard and down
she goes. What has just happened is occurring more and more often in
athletics, the athlete has just torn the anterior cruciate ligament
(ACL). In this paper I will describe ACL, how it is injured and
diagnosed, how it be repaired and what is being done to prevent ACL
injuries.
The Anterior Cruciate Ligament (ACL) is one of the two cruciate
ligaments of the knee, the other being the Posterior Cruciate Ligament
(PCL). These ligaments are the stabilizers of the knee. The ACL is a
strip of fibery tissue, which is located deep inside the knee joint. It
runs from the posterior side of the femur (thigh bone) to the anterior
side of the tibia (shin bone) deep inside of the knee. The ligament is
a broad, thick cord the size of a person's index finger. It has long
collagen strands woven together in a fashion that permits forces of up
to 500 pounds to be exerted. The function of the ACL is to prevent the
tibia from moving in front of the knee and femur. The ACL also prevents
hyperextension (or extreme stretching of the knee backward) and helps
to prevent rotation of the tibia.
The amount of knee ligament injuries have been on the rise in recent
years. Over the last 15 years, ankle sprains have decreased by 86% and
tibia fractures by 88%, but knee ligament injuries have increased by
172%. The injury usually occurs in either a slow twisting fall, a
sudden hyperextension, or a sudden hyperflexion as when landing from
jumping. When the injury occurs the athlete usually hears a "pop" and
they will have immediate swelling of the knee. When the person tries to
put weight on the leg it will feel like the knee isn't underneath the
athlete. With most injuries the type of movement will help to determine
the injury: "I twisted to the right." etc.
When ACL injuries occur there is a "popping" sound at the time of
injury and swelling within six hours. An experienced clinician can
diagnose an ACL tear with relative accuracy by a manual examination.
X-ray examination and Magnetic Resonance Imaging (MRI) is also used in
diagnosing ACL injuries. The knee joint will be instable and the
athlete will have joint pain on the inner (medial) side of the knee.
Doctors or trainers can use three different types of physical
examinations: Lachman's test, Anterior drawer test and Pivot shift test
of MacIntosh.
Lachman's test is performed by having the athlete lie on his/her
back, then passively flexing the knee of the athlete to between 20
degrees and 30 degrees. Make sure that the hamstring is relaxed or it
can produce a false test result. Holding the lower part of the
athlete's thigh in one hand and the upper part of the athlete's calf in
the other, slowly pull the tibia forward. Increased looseness in the
knee joint is indicative of an ACL injury.
During the Anterior drawer test the athlete lies on his/her back
with the knee bent to 90 degrees and the foot resting on the table.
Stabilizing the foot either by sitting on it or having someone else
hold it down, the doctor will place his/her hands around the upper part
of the calf with thumbs on the end of the thigh bone (tibal condyles),
slowly appling pressure on the posterior side of the proximal tibia.
Any looseness in the joint could indicate ACL injury.
The Pivot shift test of MacIntosh is done by having the athlete lay
on his/her back. The foot of the injured side is lifted with the leg
straight and the foot turned inward. Pressure is applied to the outside
of the knee while the knee joint is slowly bent. An ACL injury is
detected if the tibia moves out of joint at 30-40 degrees or if a clunk
is felt. One should note that this test can be very painful for the
athlete.
When an athlete has injured his/her ACL the initial treatment
involves splinting the knee, ice treatment to help reduce swelling,
elevation of the joint (just above the heart) and administration of
anti-inflammatory drugs. The athlete also needs to limit physical
activity. A non-athletic person can live with the injury using
rehabilitation and bracing. When the ACL is injured the guide wire of
the knee is gone, creating instability. Without the stabilizing actions
of the ligament, there is increased wear on the top of the tibia,
meniscal cartilages tear and the articular cartilage erodes. The
erosion will result in degenerative arthritis with grinding and pain
when climbing stairs, running or jumping. But for the active athletic
person ACL reconstruction surgery is the only solution.
Repair of the ACL by surgery can be done by open or arthroscopic
techniques. Recent advances in surgical techniques have made ACL repair
much more predictable and less traumatic to the athlete. Techniques in
arthroscopic surgery now allow surgeons to reconstruct the ligament
through smaller incisions and several smaller "stab wounds" leaving
less scarring. Techniques involve using the athlete's torn ligament
strands and incorporating them into a primary repair of the ligament
usually backed up by a portion of the athlete's patellar tendon. The
patellar tendon's middle one-third is used with a block of bone from
the patella and from the tibia. The graft is then passed through two
tunnels drilled into the tibia and the femur. The boney portions of the
graft are anchored using specially designed screws, giving a solid fix
to the graft. The graft recreates the ACL and allows early motion and
weight bearing. One problem knee injuries have is that ligaments and
cartilage have little blood supply (vascularization). This means that
they take longer to heal. Athletes can expect to return to competition
nine to twelve months after surgery.
The repair of ACL injuries has a relatively high success rate.
Approximately 1-2% of people will have some degree of dissatisfaction
with their surgery. The leading causes of dissatisfaction are:
arthrofibrosis (scar tissue), deep venous trombosis (blood clots in leg
veins), poor knee motion, infection and injury to the patella.
How can athletes prevent ACL injuries? Like most injuries they are
not always preventable. Certain things can be done to help prevent the
risk of injury. Strengthening the muscles around the knee that act as
shock absorbers and joint stabilizers is of key importance. Strong
thigh muscles will help keep the knee in position. Doing half squats or
using a leg machine will work the thigh muscles. Running hills and
stairs will strengthen both quadriceps and hamstrings. Riding a bicycle
three times a week either indoors or outdoors will help. Make sure that
the seat is high enough to avoid excessive knee bending. Water aerobics
is also a great way to strengthen joints without a lot of stress. A
knee bend resistive exercise program done by The United States Ski Team
has resulted in an 80% decline in serious knee injuries. The program
uses a single stance one-third knee bend going from 30 to 80 degrees at
a steady rate for three minutes, working up to five minutes on each
leg. Sport band (elastic cord) can be used to increase resistance when
initial levels are achieved.
The anterior cruciate ligament is the main guide to knee
stabilization. Fortunately injuries to the ACL are now much more
treatable and athletes are returning to performance at a greater rate.
All athletes need to be aware of the risk of ACL injuries but they also
need to know if it does happen, it's not the end of their athletic
career.
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