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DR. MORA'S KNEE INJURY
PROGRAM
Meniscus and Articular Cartilage Problems
Steve A. Mora, MD
Member of the American Academy of Orthopaedic Surgeons
 Introduction You
have injured your knee. This is one of the most common orthopaedic injuries seen
in our practice. Many knee injuries
occur after a sports related accident but they may also occur after a simple fall
or even during daily activities such as bending or squatting down. Perhaps
in your case, you have been living
with the pain for years and in fact you cannot remember the last time your knee
felt completely normal. Simple activities
such as a short walk at the park, walking up
and down the sideline of your child's football game, or getting in and out of
your car have become difficult. Whatever the scenario, the result is the same;
your knee pain is making life difficult or maybe its just not physically enjoyable
anymore.
Anatomy
The femur is the upper portion of the knee joint.
Its ends are lined with a smooth thin covering
called articular cartilage.
This surface lining allows smooth and practically frictionless motion. The
tibia below is also lined with articular cartilage on its surface. These
bones along with the
patella (knee cap) will articulate together to form the knee joint. There are 2
"shock
absorbers" called meniscus sandwiched between these two bones. These are made out of the same
soft tissue material,
fibro-cartilage, as
that which makes up the tip of your nose.
These
crescent-shaped
structures, medial and lateral meniscus, sit on the surface of the tibia.
Because of their poor blood supply,
once torn these menisci rarely heal.
For this reason, torn meniscus are usually treated by removing the torn pieces
rather than stitching the tear together. The anterior cruciate ligament (ACL), posterior cruciate ligament
(PCL), medial collateral ligament (MCL) and lateral collateral ligament (LCL)
are the 4 major ligaments. Their function is to keep the
knee joint "in line" or stabilized by
maintaining the anatomical alignment of the femur and the tibia. The ACL
is frequently torn in sports and requires complete replacement (reconstruction)
instead of suturing together.
What kind of cartilage does the knee joint contain?
Two types: Meniscus and Articular
1. Meniscus cartilage is located between the
femur and tibia. It serves to cushion and lessen friction at the junction
of those two bones. They also serve to better distribute the load from
walking and running. These soft tissue structures have poor blood supply
and easily
become torn.
2. Articular cartilage is the slick, durable,
pearly white, substance that covers the ends of the femur, patella, and tibia.
It allows smooth gliding and with almost no friction. Articular
cartilage usually takes more force to injure than meniscus. It is not
uncommon following major trauma to the knee. This type of cartilage also has poor healing capacity once
injured. This is also the type of cartilage that becomes worn out in
osteoarthritis as we age.
Of the two types, meniscus is
more likely to be torn. Knee arthroscopy for the management of
meniscus tears is the most common Orthopaedic procedure performed today.
But either or both types of cartilage can be damaged by trauma, cumulative forces, or the aging process.
Articular cartilage treatment is much more involved.
What causes tears
?
Meniscus can tears are frequently seen following
a bending or squatting movement.
Cartilage tears can often occur
in conjunction with other knee injuries, such as ligaments. There are also conditions where the cartilage becomes damaged for unclear reasons and with
minimal trauma such as in osteochondritis dissecans (OCD) where the
cartilage develops a crater like lesion. Osteoarthritis is a cartilage
problem and is due to wear and aging.
Why is there pain?
Usually a patient with a torn meniscus will feel
pain and grinding along the inner side of the knee joint. If it's a significant tear, there may be other symptoms, such as
stiffness, popping, clicking and locking. The more displaced or
“out of position” the torn fragments are, the more severe the symptoms will be.
The surgery goal is to remove these torn fragments.
**"The Take Home Message" ** It is thought that when a meniscus is
damaged, the
knee is painful for a couple of reasons. First, the torn fragments are loose,
they move
in and out of place, causing clicking, popping, locking, swelling and irritation.
Second, the knee has lost meniscus support (remember that they are like "shock
absorbers"). When a portion of the meniscus
is torn it can no longer provide normal dampening
of joint forces. The loss of support is proportional to the size of the tear.
Arthroscopic surgery can usually
improve the knee pain because the painful fragments are snipped out or removed.
However, the meniscus became irreversibly damaged when it was torn and not when
the fragments were excised. The
torn meniscus does not regenerate itself, therefore, the small area with the
tear will remain abnormal permanently. In cases of massive
tears, loss of "meniscus support" becomes significant and despite
surgery the knee remains painful to some degree.
Because of this fact, we cannot
guarantee that your arthroscopic surgery will be 100% successful. The
greater the loss of meniscus tissue, the greater the risk of having persistent
pain or future degeneration (i.e. osteoarthritis). Studies have shown that
if a total meniscus is torn and removed, the knee is destined to develop
arthritis in 12-15 years. The good news is that
the
long-term
results
of arthroscopic partial meniscectomy is excellent. Also, it is rare to have a
large tear and actually most of the
time the tears are small and therefore respond well to surgery.
How is the injury diagnosed?
After the exam,
an x-ray is usually done to check for arthritis, spurs, or calcifications.
An MRI can be performed to assist in the diagnosis as well as
identify cysts and degenerative changes of the joint.
How are cartilage tears treated and what are the options? Firstly, there is no rush.
The surgery is
elective. It may be done any time.
Think about a tear like a pebble in your shoe. It
will be uncomfortable and even painful but satisfactory activity is sometimes achievable
without having to take the pebble out. The treatment is predicated on the intensity of the symptoms
but not
merely the existence of a positive MRI. Therefore, with tears that cause considerable
pain, the treatment may include surgery.
Initial measures
to reduce pain include:
ice and non-steroidal anti-inflammatory drugs (NSAIDs). If
the tear is not substantial enough for surgical intervention, then the patient
may begin exercising to restore strength, range of motion, and overall
function. There are no restrictions. The activity is guided by the
pain.
 Knee Arthroscopy and Meniscus/Articular
Cartilage Treatment. This
option should be selected for those individuals who's symptoms do not allow them to reach their
functional goals.
Today, the operation is performed using two small incisions, each 1/2 inch long in the
front of the knee.
It is performed as an outpatient and usually with
a combination of local anesthetic with a intravenous sedation (MAC Anesthesia). Meniscus
repair (stitching the edges of the torn meniscus together usually is done in
young patients with a clean cut type of tear. Most of the time the torn
fragments are cut out.
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