Joint Surface InjuriesOsteochondral injury implies an injury to the joint surface or articular cartilage with some of the underlying bone. Chondral injuries involve only the articular cartilage. BackgroundSometimes 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.
SymptomsThe 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. DiagnosisThe 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. TreatmentMost 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.
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.
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.
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