Osteochondral
injury implies an injury to the joint surface or articular cartilage
with some of the underlying bone. Chondral injuries involve only
the articular cartilage.
Sometimes after a jarring or twisting injury of the knee, rather
than tearing a cartilage or a ligament, the articular cartilage
may be damaged. It may also occur in conjunction with these other
injuries. The result can be a loose fragment of articular cartilage
which leaves an exposed area of bone in the knee (a crater in the
otherwise smooth joint surface). Alternatively the damage may be
a breaking up or splitting, but not complete loss of, the articular
cartilage in any area of the knee.
This can be a potentially serious condition, particularly in young
adults, because it may give rise to long term problems. It is difficult
to cure, and in the long term can increase the risk of developing
significant osteoarthritis.
« A diagram of a chondral indury »
« An arthroscopic view of a chondral
injury »
The symptoms of chondral injury tend to be pain, clicking, catching
and swelling. Quite often the pain is well localized to the area
of damage. Occasionally, it is difficult to say exactly where the
pain is arising from, and the knee feels generally uncomfortable.
If the injury has resulted in a fragment of the joint surface cartilage
floating around the knee there can also be symptoms of a loose body,
with clunking, catching and the feeling of something loose in the
knee.
The diagnosis of a chondral injury in the knee joint can be made
on the story of an injury along with examination of the knee which
may reveal nothing more than discomfort and swelling.
X-rays are useful if there is a small fragment of bone as well as
a fragment of articular cartilage (i.e. osteochondral damage). If
not, the x-rays will probably be normal.
An MRI scan will show up most chondral injuries. Sometimes if there
is a suspicion of such an injury but x-rays and MRI scan are negative,
arthroscopic surgery is required both to confirm the diagnosis and
to instigate treatment.
Most acute chondral injuries will be treated with arthroscopic surgery
to either remove or replace the damaged fragment.
In general the only repairable injuries of this type are where there
is quite a large chunk of articular cartilage with a sliver of bone
(an osteochondral fracture) which can be pinned back in place.
If the fragment has to be removed and it leaves behind a crater
in an important part of the knee with bare bone in the base, it
will not heal up with normal joint surface cartilage. It may heal
up with fibrocartilage or scar tissue in the base giving some sort
of smooth covering. This type of covering can be encouraged by making
some small holes in the bone. By encouraging bleeding into the area,
scar tissue will form. This technique is sometimes referred to as
microfracture.
« A diagram of microfracture »
If persistent problems arise because of a defect in the articular
cartilage, then there are a number of specialised techniques which
may be performed, but for which not everybody is suitable.
Osteochondral autograft transplantation surgery (OATS), also called
mosaicplasty, is a technique to remove healthy plugs of bone and
articular cartilage from one area of the knee (where it is required
less) and to put them into the damaged area.
« A diagram of osteochondral autograft
transplantation surgery (OATS) »
Autologous chondrocyte implantation (ACI) involves the culture of
chondral (articular cartilage) cells removed from your knee, and
then re-implanted into the defect. Although this sounds like an
ideal technique it is still largely experimental. It is still not
clear whether it is fully effective because in a lot of cases biopsies
taken a year from surgery have shown that it is simply scar tissue
which has formed in the crater, rather than the desired articular
cartilage.
« A diagram of autologous chondrocyte
implantation (ACI) »
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