Although symptoms may not appear until later in life,
articular cartilage problems are very common. Painful osteoarthritis
develops when this smooth, gliding surface on the end of the bone
has lost its cushioning, deformity develops, and bone rubs on bone.
Damage may occur as the result of a sudden injury or wear and tear
over many years. There are some people with damaged articular cartilage
who display few symptoms and may not develop osteoarthritis until
they are elderly.
The development of ostearthritis depends
on several factors:
The patient's age when the degeneration
starts
The
patient's activity level and weight
The presence of ligament damage
Articular cartilage problems can be
particularly difficult to treat because the onset, while occasionally
sudden, often occurs gradually and thus is not immediately detected.
What is articular cartilage and
what does it do?
There are two types of cartilage in the human knee:
Meniscus
cartilage - This is the cartilage most commonly referred
to when the term "torn cartilage" is used. These two
rubbery shock absorbers sit between the upper bone of the thigh
(femur) and the large bone in the lower leg (tibia).
Articular
cartilage - This cartilage is the shiny, white surface that
covers the ends of most bones. Articular cartilage protects
the ends of bones and allows the joints to glide smoothly with
less friction. It also helps to spread the loads applied to
a joint. This covering is only a few millimeters thick and it
has no blood supply to facilitate the healing process. Therefore,
if it gets damaged, there is very little capacity for healing.
What is an articular cartilage
injury?
An articular cartilage injury, or chondral injury,
may occur as a result of a pivot or twist on a bent knee, similar
to the motion that can cause a meniscus tear. Damage may also be
the result of a direct blow to the knee. Chondral injuries may accompany
an injury to a ligament, such as the anterior cruciate ligament.
Small pieces of the articular cartilage can actually break off and
float around in the knee as loose bodies, causing
locking, catching, and/or swelling. More often, there is no clear
history of a single injury. The patient's condition may, in fact,
result from a series of minor injuries that have occurred over time.
Articular cartilage also wears down as a person ages.
Chondral damage is graded from mild
to severe, and all grades can have characteristics of osteoarthritis.
Grade I - The cartilage "blisters"
and becomes soft in the earliest form of damage.
Grade II and III -
As the condition worsens, the cartilage may become fibrillated
(it has a shredded appearance). The grade of injury
depends on the size of the involved area and how much of the cartilage
thickness is worn down. Noise as the knee bends, called crepitus, may be present.
Grade IV - The cartilage
may wear away completely, leaving the underlying bone exposed
in small or widespread areas. When the involved areas are large,
pain usually becomes more severe, causing a limitation in activity.
