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Meniscal Injuries
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A meniscus is
basically the shock absorber of the knee. Normally, we are each born with two
menisci in each knee. One is situated toward the inside aspect of the knee
and is called the medial meniscus. The other is located on the outside aspect
of the knee and is called the lateral meniscus. These have been described as
C-shaped or semi-lunar. They are only a few millimeters thick and have a
rubber-like consistency. This helps them to absorb the shock of weight going
across the knee joint during impact activities such as running and jumping and
also non-impact activities such as walking, climbing and squatting. Complete
excision of a meniscus leads to increased stress being transmitted to the ends
of the femur (thigh bone) and tibia (shin bone) as they articulate against
each other at the knee joint. The resulting increased stress on the surface
of these bones is thought to predispose them to wear out prematurely leading
to degenerative arthritis (also called osteoarthritis). |
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Although important, a
meniscus can tear and become painful. Sometimes it can tear in a way
that produces a flap of tissue, which displaces and can actually be a block to
motion of the knee. This can cause the knee joint to lock in one
position, and can be extremely painful. |
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Years
ago, we did not have arthroscopic surgical techniques to address this problem,
and open surgery was the only option. This typically resulted
in the excision of the entire meniscus, not just the torn part. Subsequently,
many people
started developing degenerative arthritis of that knee about 15 years after
having their entire meniscus excised. |
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With arthroscopic
procedures, visualization and access to the meniscus is much improved over the
traditional open surgical approach. As a result, only the torn portion of the
meniscus need be excised, leaving the remaining functioning meniscus in
place. This greatly decreases the loss of function of the meniscus. It is
important to realize that the torn part of the meniscus is not functioning
anyway, yet causing symptoms. Removal of the torn part will not result is
restoration of function, but it will lead to decreased symptoms, usually
allowing return to normal activity. |
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Why not repair the
torn meniscus? The meniscus actually has a very poor blood supply. As a
result, most repairs will not heal and continue to cause problems. A
small percentage of
meniscal tears do maintain adequate blood supply, and attempts are made to repair them. |
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As mentioned above,
only a certain percentage of menisci are going to heal if we repair them. In
fact, only 10-15% of all meniscal tears fall into this category. Although the
meniscus may be saved, recovery from meniscal repairs is a lot slower than
recovery from partial meniscal excision. If the meniscus is partially
excised, there really is no repair to protect. Therefore, as the swelling and
stiffness associated with surgical intervention diminish, one may begin to
return to normal activity. On the other hand, if a meniscus tear is repaired,
we have to protect that repair until the meniscus heals. This typically takes
3 to 4 months. During this time there are restrictions placed on activity.
Because of this, return to normal function after a meniscal repair operation
is much slower than after partial meniscal excision. |
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Arthroscopic picture of a normal medial meniscus: |
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Flap tear of the medial meniscus of the
right knee: |
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Same knee after arthroscopic excision of
the torn portion of the medial meniscus: |
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What if one loses an
entire meniscus? A massive irreparable meniscal tear can lead to loss of the
entire meniscus. Fortunately, technology has advanced to the point of allowing
us to perform meniscal transplantations. In this procedure, a cadaveric
meniscus is transplanted into a knee lacking that structure. Only certain
knees are candidates for this promising technique, however. Dr. Ilahi is one
of only a handful of surgeons in the Houston area with experience in this new
and technically demanding operation. |
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