Anterior Cruciate Ligament (ACL) Injuries



About ACL Injuries



Knee injuries are common among active kids, especially athletes, and a
torn anterior cruciate ligament (ACL) — a ligament that helps give the
knee its stability — is one of the most common types of knee injuries.

Kids who play contact sports (like football and basketball) or
so-called "cutting" sports (like soccer and baseball that feature swift,
abrupt movements such as pivoting, stopping, or turning on a dime) are
most likely to get ACL injuries.

The injury also happens when a child jumps and lands on the feet with
knees straight or "locked"instead of flexed, putting excessive pressure
on the knee joint and causing the ACL, a rope-like band, to tear or
break apart.

Teenage girls are four times more likely than boys to tear an ACL,
either from hormones that loosen the ligament and make it more
susceptible to breaks or a natural inclination to land with straight
knees.

ACL injuries can be very painful, causing a child to be unsteady on
the feet and have difficulty walking. Depending on the age of the child
and the severity of the injury, a torn ACL often requires surgery in
addition to 6 to 12 months of rehabilitation.

What an ACL Does



The ACL is one of the four main ligaments in the knee joint that
connect it to the shinbone (tibia) and thighbone (femur). It is located
deep within the joint, behind the kneecap (patella), above the shinbone,
and below the thighbone.

Together with the PCL (posterior cruciate ligament), which crosses
over it to form an "X," the ACL helps prevent the overextension of the
knee joint from front-to-back or side-to-side.

Specifically, the ACL keeps the shinbone in place and prevents it
from moving too far forward and away from the knee and thighbone. It
also provides stability when rotating the shinbone.

Signs and Symptoms





Kids with a partially or completely torn ACL may or may not have symptoms, depending on the severity of the injury.

Most will have some instability when walking, feeling "wobbly" or
unable to bear weight on the affected leg. Oftentimes there is pain,
which can be very intense, and swelling of the knee joint, which can
happen within 24 hours of the tear.

Many kids, especially those who are familiar with the injury or have
torn that very same ligament before, report hearing a "pop" sound — the
sound of the ligament tearing. Others also report the knee feels "less
tight" or less compact than it was before.

A child who has injured a knee — whether out on the field or at home —
should stop all activity (to prevent further injury) and seek immediate
medical care. In the meantime, keep the area iced and elevated as much
as possible to reduce swelling. Do not let the child bear weight on the
knee.

Diagnosis



At the doctor's office or emergency room, doctors will perform
physical exams and imaging tests to determine if there is a knee injury
and, if so, how severe it is.

In addition to tearing the ACL partially or completely, some kids
(depending on their age and the rigidity of the bones) may tear off a
portion of the top of the tibia along with the ACL.

These tests can help diagnose an ACL injury:

• Lachman test. During this exam, a child will lie
  down flat on his or her back with the affected knee lifted and flexed at
  a 20- to 30-degree angle. The doctor then places one hand on the back
  of the shin and the other on the top of the thigh, applying pressure to
  move the shin forward. If it moves too far forward, it can signal a torn
  ACL.
  
• Pivot-shift test. As in the Lachman test, a child
  lies down flat, but instead of flexing the knee, flexes the hip at a
  30-degree angle so the leg is pointed up, straight, and outward. The
  examiner grasps the ankle and underneath the shin bone and attempts to
  rotate the tibia to see if there is any interior rotation beyond the
  normal limit.
  
• Anterior drawer test. During this test, the hip is
  flexed at 45 degrees and the knee at 90 degrees. The examiner grasps the
  back of the shin, just below the knee, placing index fingers on
  hamstring tendons and thumbs on the side of the kneecaps to feel any
  shift of the knee joint and surrounding areas while attempting to pull
  the tibia forward.
  

To properly diagnose ACL injuries, doctors usually perform these tests in combination or in addition to other physical exams.

While X-rays might be taken to determine the extent of the injury,
they only image bone and, therefore, can only confirm the presence of
bone fractures in the knee. An MRI,
which images tissue (like ligaments and muscles), can confirm a partial
or complete ACL tear so some doctors will order one to confirm a
diagnosis.


Treatment



Treatment of ACL injuries depends on the age of the child and the
type of injury. Age is important because it will determine whether a
child has intra-articular reconstructive surgery (which takes place inside the knee joint) or extra-articular surgery (which takes place outside the joint).

Two different approaches are needed because most kids who are still
growing should not have intra-articular surgery due to the potential
harm to growth plates. Growth plates are the developing
tissue on the ends of long bones, like the tibia and femur. Kids who
are still growing have "open" growth plates, while those who have
reached skeletal maturity have "closed" growth plates.

When a child stops growing, the growth plate hardens (ossifies) along
with the rest of the bone. Girls tend to stop growing earlier than
boys; their growth plates usually close around ages 14 to 15, while
boys' growth plates close later, at around ages 16 to 17.

A child who has reached skeletal maturity will probably undergo
intra-articular reconstructive surgery. This procedure involves drilling
a small tunnel down through the femur to reach the inside of the knee
joint. This is the only way to get to the center of the knee, behind the
kneecap. A second tunnel is made just below the knee, up through the
tibia.

Surgeons replace the torn ACL with tissue from the patient's own body
(usually a kneecap or hamstring tendon) or with donor tissue (called an
allograft) from the Achilles tendon in the foot. The new ACL tissue is
fed through the tibia and femur tunnels and is secured in the proper
area with screws or other fixtures.

Extra-articular surgery does not seek to replace a torn ACL (thus, it
doesn't require tunneling of the tibia or femur), and instead focuses
on tightening the iliotibial tract, a thick band of
tissue that spans the leg from the lower pelvis to the bottom of the
shinbone. Tightening this tissue over the kneecap helps to stabilize the
knee and prevent the tibia from moving too far forward.

After surgery, a child will need to walk with the assistance of
crutches, limit physical activity, and wear a full-leg brace for 4 to 6
weeks, depending on the severity of the injury.
Rehab and Recovery



Recovery from ACL surgery is a lengthy process that can take from 6
months to a year. Rehabilitation ("rehab") therapy is needed to help
heal the knee and to:

• restore range of motion
  
• regain strength in the knee, thigh, and shin muscles (and prevent atrophy, the breakdown of muscle tissue)
  
• reduce pain and swelling
  
• improve balance
  

Most kids undergo rehab at a center three times a week, with daily
exercises they practice at home. Accelerated rehab programs require more
frequent therapy and speed up recovery to 4 to 6 months.

In the early stages of recovery, a child will have to wear a leg
brace, followed by a knee brace, to reduce the risk of reinjuring the
knee. Keeping the knee iced and elevated can help to reduce swelling.
Over-the-counter or prescription painkillers and anti-inflammatory
medicine can help kids deal with the pain and feel more comfortable.

While most sports are off limits — especially the activity that
caused the injury in the first place — kids can do some low-impact
activities that may be fun and even therapeutic, like swimming, bike
riding, or protected running. Talk to your doctor about what activities
might benefit your child.

Helping Your Child Cope



Being told that you can't do the things you love — like running or
playing football, field hockey, or softball — can be a devastating blow
to any child. Kids recovering from an ACL injury may feel angry,
frustrated, or even depressed, especially if they're no longer
participating in team sports with their friends.

But in the meantime, there are ways to still feel like part of the
team. Keeping score, being a coach's assistant, or bringing water to the
games may help. If your child doesn't want to do these, suggest
starting a hobby, like playing the guitar, painting, drawing, or another
sedentary activity that won't put too much strain on the knee.
Low-impact activities, like swimming, are another option.

In time, your child can again do the things he or she loves. But if,
during recovery, your child continues to feel angry or depressed,
consider talking to a school psychologist or counselor, who may be able
to help your child cope and look ahead to better days.