MENISCUS INJURY
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Introduction
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Anatomy
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Causes
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Symptoms
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Diagnosis
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Treatment
Introduction
The meniscus is a commonly injured structure in the knee. The
injury can occur in any age group. In younger people, the meniscus is
fairly tough and rubbery, and tears usually occur as a result of a fairly
forceful twisting injury. In older people, the meniscus grows weaker with
age, and meniscal tears occur as a result of a fairly minor injury, even
from the up and down motion of squatting.
Anatomy
What is the meniscus and what does it do?
There is
a meniscus on either side of the knee
joint. The meniscus acts like a gasket between the femur and the tibia to
spread out the weight being transferred from the femur above to the tibia
below. The knee anatomy section points out that articular cartilage covers the ends of
the bones that make up the joint. The articular cartilage surface is a
tough, very slick material that allows the surfaces to slide against one
another without damage to either surface. This ability of the meniscus to
spread out the force on the joint surfaces as we walk is important because
it protects the articular cartilage from excessive forces occurring in any
one area on the joint surface. Without the meniscus, the concentration of
force into a small area on the articular cartilage can damage the surface,
leading to degeneration over time.
Remember also that the meniscus helps with the stability of the knee
joint. The meniscus converts the tibial surface into a shallow socket. A socket configuration is more stable
than a flat surface. Without the meniscus, the round femur would be free to slide on top of the flat
tibial surface.
The meniscus can be torn in several ways. The entire inner rim of the
medial meniscus can be torn in what is called a buckethandle tear. The meniscus can
also have a flap torn from the inner
rim, or the tear can be a degenerative
type tear where a portion of the meniscus is frayed and torn in multiple
directions.
Causes
How does the meniscus cause problems in the knee?
Meniscus injuries can occur in any age group, but the causes are somewhat
different for each age group. In younger people, the meniscus is a fairly
tough and rubbery structure. Tears in the meniscus in patients under the
age of thirty usually occur as a result of a fairly forceful twisting
injury. In the younger age group, meniscal tears are more likely to be
caused by a sport activity.
In older people, the meniscus grows weaker with age. The tissue that
makes up the meniscus becomes degenerative
and is much easier to tear. Meniscal tears in the older age group occur as
a result of a fairly minor injury, even from the up and down motion of
squatting. Degenerative tears of the meniscus are commonly seen as a part
of the overall condition of osteoarthritis of the knee in the older population. In many cases,
there is no one associated injury to the knee that leads to the meniscal
tear.
Symptoms
What does a torn meniscus feel like?
The most common problem caused by a torn meniscus is
pain
. The pain may be felt along
the joint line where the meniscus is located or may be more vague and
involve the whole knee. If the torn portion of the meniscus is large
enough, locking may occur. Locking
simply refers to the inability to completely straighten out the knee. Locking occurs when the fragment of
torn meniscus gets caught in the hinge mechanism of the knee and will not
allow the leg to straighten completely. (Imagine sticking a pencil between
the hinges in a door and trying to close it.)
There are
long term effects of a
torn meniscus as well. The constant rubbing of the torn meniscus on the
articular cartilage may cause wear and tear on the surface, leading to
degeneration
of the joint. The knee
may swell with use and become stiff and tight. This is usually because of
fluid accumulating inside the knee joint - sometimes called
water on
the knee. This is not unique to meniscus tears, but occurs whenever
the knee becomes inflamed.
Diagnosis
How do we look into this problem?
Diagnosis begins with a history and physical. The examination
will try to determine where the pain is located, whether or not locking has
occurred, and if you have any clicks or pops as the knee is moved. X-rays
will not show the torn meniscus. X-rays are mainly useful to determine if
other conditions are present. The MRI scan is very good at showing the
meniscus. The MRI (Magnetic Resonance Imaging) machine uses magnetic waves
rather than x-rays, to show the soft tissues of the body. With this
machine, we are able to "slice" through the area we are interested in very
clearly. Usually, this test is done to look for injuries, such as tears in
the menisci or ligaments of the knee. This test does not require any
needles or special dye, and is painless. Here the MRI scan shows a tear in the meniscus. If there is a
uncertainty in the diagnosis following the history and physical examination,
or if other injuries in addition to the meniscal tear are suspected, the MRI
scan may be suggested.
If the history and physical examination strongly suggest that a torn
meniscus is present, then arthroscopy
may be suggested to confirm the diagnosis and treat the problem at the same
time. Arthroscopy is a type of an operation where a small fiberoptic TV
camera is placed into the knee joint, allowing the orthopedic surgeon to
look at the structures inside the knee joint directly. The arthroscope
allows your doctor to actually look into the knee joint and see the
condition of the articular cartilage, the ligaments and the menisci .
Treatment
How do we treat this problem?
Initial treatment for a torn meniscus usually is directed towards
reducing the pain and swelling in the knee. Your physician may recommend
crutches for resting the knee for several days and suggest ice to reduce the
pain and swelling. If the knee is locked and cannot be straightened out,
surgery may be recommended as soon as reasonably possible to remove the torn
portion that is caught in the knee joint. Once a meniscus is torn, it will
most likely not heal on its own.
If the symptoms continue, surgery will be required to either
remove the torn portion of the meniscus or to repair the tear. Most
meniscus surgery today is done using the arthroscope. Small
incisions are made in the knee to allow the insertion of a small TV camera
into the joint. Through another small incision, special instruments are
used to remove the torn portion of
meniscus while the arthroscope is used to see what is happening. In some
cases, the meniscus tear can be repaired.
The arthroscope is used to view the torn meniscus. Sutures are then placed
into the torn meniscus until the tear is repaired. Repair of the meniscus
is not possible in all cases. Young people with relatively recent meniscal
tears are the most likely candidates for repair. Degenerative type tears
in older people are not usually repairable.
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