Meniscal Tears of the Knee
 GENERAL
The most common problem of the knee is related to the semilunar cartilage (meniscus). There are two of these in each knee. One is medial (on the inside) and the other is lateral (on the outside) of the knee. Each appears like a
crescent moon and is attached on its outer edge to the knee capsule and at each
end to the tibia by ligament attachments. The meniscus is responsible for a
four-fold increase in surface contact between the bones of the knee (tibia and
femur). The meniscus also aids in shock absorption between the joint surfaces
and aids in knee stability and lubrication. Complete loss of the meniscus is
known to cause eventual arthritis. Each meniscus is made of cartilage. The
outside one third has a blood supply and
the capacity to heal. The inner
two-thirds of the meniscus has more limited capacity
to heal. A tear of the
meniscus may occur following major trauma or none at all.
This depends on the
age of the individual and prior injury and activities. Not all
tears are
symptomatic, and many older patients are unaware they have a tear.
Symptomatic
tears are those which cause pain, locking, stiffness, or recurrent swelling.
Untreated symptomatic tears may cause permanent damage (arthritis), because the
torn meniscus rubs on the surface of the joint like "sand in a ball-bearing". These tears are best treated early.
DIAGNOSIS
Diagnosis of a meniscal tear is often straight forward on physical exam. In
other cases, especially if symptoms are subtle or intermittent, or coexist with
arthritis, diagnosis is more complicated. In this case MRI (magnetic resonance
imaging) may demonstrate the presence or absence of significant meniscal tears.
MRI uses a large magnetic field and radio waves (no X-ray) to create multiple
pictures of the knee. MRI can detect meniscal tears and ligament injuries with
greater than 95% accuracy. MRI is a very expensive test. It is therefore
reserved for cases where physical exam and symptoms are not typical. It
generally requires 30-40 minutes and may be hard to perform in patients with
claustrophobia who have difficulty tolerating the confines of the scanner.
Magnetic metals embedded in the body are a contraindication to performing the
test. Very heavy patients may require use of a special scanner made to
accommodate their size and weight, or MRI may just not be possible. An Arthrogram is an older technique used to demonstrate meniscal tears. It is performed by
injecting an iodine containing contrast material into the knee followed by
multiple plain X-ray images taken to show the "dye" within the
meniscus where it doesn't belong. This is a more invasive test requiring
injection of contrast, and cannot be performed in patients with iodine or
shellfish allergy. It unfortunately has only an 85% accuracy in demonstrating
meniscal tears, and is even less reliable in documenting ligament injuries.
SURGERY
Meniscal tears are now treated arthroscopically. The Arthroscope is a
small fiberoptic telescope used to look into the knee. Although general
anesthesia is often used, arthroscopy may be performed with regional anesthesia
("local block") or even local anesthesia with IV sedation and little
discomfort. Total relaxation is required to fit even the small instruments
required into the knee and perform the necessary surgery. The geometry of
meniscal tear and the age of the patient dictate meniscal tear repair vs.
partial resection. In general, tears in young patients at the outer edge of the
meniscus may be repairable. Older patients generally have tears
which are due to
wear and tear, and are less likely to be repairable. The healthiest knee is one
with all its original parts. Meniscal preservation is therefore attempted
whenever possible. Meniscal repair requires suture of the torn parts together.
This can be performed arthroscopically, but may require a secondary incision
utilized to protect important nerves and vessels. If meniscal tear
accompanies ligament injury, then ligament reconstruction is recommended.
This is especially important if meniscal repair is performed.
RECOVERY
The time required to recover from a meniscal tear is variable. This is
because of the variability of tear geometry. Associated ligament injury or
surface damage to the joint surface may affect recovery. In addition,
partial meniscectomy requires little protection after surgery whereas repair of
a torn meniscus necessitates protective rehabilitation for 3-4 month
REHABILITATION
After
Arthroscopy
describes early post operative treatment after meniscectomy or repair. Simple partial meniscectomy generally needs no formal physical therapy.
A few days to a week of protected weight bearing with crutches and rapid
restitution of normal activities is encouraged. Occasionally therapy is
needed to aid the return to normal motion and strength, but this is relatively
rare. Meniscal repair requires protected weight bearing with bending, but
normal weight bearing on an extended knee rapidly after surgery. Return to
normal sports after meniscal repair is generally possible after about 4 months.
CONCLUSION
Not all tears of the meniscus require surgery. Only some knee problems
are related to a torn meniscus. Meniscal tears may
become symptomatic
after an acute injury or gradually with no known injury. Symptom-free
tears may become symptomatic
with aggravating activities.
A symptomatic tear treated arthroscopically usually results in a return to full
activity.
Rehabilitation following Meniscal Repair takes about 4 months until complete recovery.
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