Anterior Cruciate Ligament Injuries


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). 

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
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 he/she 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
unstable 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
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
applying pressure on the posterior side of the proximal
tibia. Any looseness in the joint could indicate ACL

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 thrombosis (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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