> ACL Tear
What is the ACL?
The ACL (anterior cruciate
ligament) is the smallest of the four main ligaments
in the knee but it is the primary stabilizer for rotational
movement. It connects the thighbone (femur) to the shinbone
(tibia) in the center of your knee, limiting rotation
and forward movement of the shinbone. Without an ACL,
the knee would be unstable and could dislocate during
activities that involve twisting.
When the shinbone and thighbone rotate too far in opposite
directions or the knee is bent in the wrong direction,
the ACL can be torn, or, depending on the force of the
injury, sprained. It is estimated that 50 percent of
ACL tears are accompanied by cartilage tears, and 20
to 30 percent involve other ligament damage. The ACL
and the MCL (medial collateral ligament) are often injured
at the same time.
Quick directional changes while running
cause most ACL injuries. When a basketball player, running
down the court, plants his foot hard to change direction,
his knee buckles as the thighbone and shinbone move
in opposite directions, tearing the ACL. Sports like
basketball, soccer, and skiing often cause these non-contact
ACL injuries. Football players seem to be at the greatest
risk for multiple knee injuries like combined ACL, MCL,
and cartilage damage.
Some people with a completely torn
ACL are able to build their muscle strength enough to
resume normal activities without surgery. While activities
of daily living may be possible without an ACL, it is
less likely that patients will be able to return to
cutting and twisting sports. Still, the non-operative
option exists, and having surgery or forgoing it is
partly a personal choice. Those who are not very active
may choose a strengthening program instead of surgery,
since the injury is not likely to interfere with their
daily activities. Such a program takes about four months
to complete. However, here is a statistic that should
be considered: about 65 percent of all patients with
a torn ACL will eventually develop a torn meniscus,
which may predispose them to an early onset of arthritis.
Active, athletic people are more likely to opt for surgery,
so that the knee can be repaired and rehabilitated and
they can return to their activities. Rehabilitation
following surgery can take as little as three months
but usually takes one year, and requires a commitment
of at least 45 minutes three days a week. But the success
rate is about 90 percent, meaning that most people will
be able to return to their active lifestyles after an
ACL reconstruction. An untreated ACL may leave you unable
to trust the stability of your knee. It may continue
to give way, putting you at risk for further injury
to other knee structures. An untreated ACL injury often
causes cartilage damage that can lead to the early onset
There are three parts to an orthopedic
evaluation: medical history, a physical exam, and tests
that your physician may order.
will likely ask you how you injured your knee, how it
has been feeling since the injury, and if your knee
has been previously injured. Physicians also typically
ask about other conditions, such as diabetes and allergies,
and medications currently being taken. The doctor also
may ask about your physical and athletic goals
information that will help him decide what treatment
might be best for you in achieving those goals.
A physician usually can make an early
assessment of an injury by feeling around the area,
but because the ACL is deep inside the knee, it is difficult
to feel around in search of pain or tenderness. Instead,
there are two common tests to determine the existence
of an ACL injury and its severity that can be performed
in your physician's office.
Lachman test, which determines instability of the ACL.
In this, the leg is held slightly bent and the physician
pulls on the lower leg (tibia). If the leg moves significantly
more than the other, uninjured, knee, that may signify
a torn ACL. A hand-held instrument called an arthrometer
may also be used to measure the stability of the knee.
the knee bent 90 degrees, the doctor will pull the tibia
forward in what is called an anterior drawer test. If
the tibia moves excessively forward, that would strongly
suggest a torn ACL.
Should your physician require a closer look, these tests
may be conducted:
(magnetic resonance imaging) has an accuracy rate of
nearly 90 percent in determining whether an ACL has
been torn and to what extent it has been damaged. It
is not very good, however, at detailing a partial tear.
in which the doctor inserts a small camera into your
knee, is the best way to examine a partial tear. Arthroscopy
allows the physician to examine the ACL to determine
the extent of the tear and if reconstructive surgery
is needed. Though less painful than some procedures,
arthroscopy is not pain-free. If your ACL is torn, it
is usually reconstructed at the same time as the arthroscopic
exam, and you may be required to stay overnight.