What is Osteochondritis dissecans? To know more, you need to know the anatomy of the knee. Read on…

Anatomical background
The ends of three bones inside the knee joint are lined by articular cartilage. This smooth spongy tissue is responsible for the smooth and pain less movement. In this condition, which can occur in children and adults, there is a gradual flaking off this tissue (cartilage) with the underlying bone due to degeneration. This exposes bone, which scrape against another causing pain.The lesion is located at the lateral end of the medial femoral condyle.

Symptoms& Signs
Pain and swelling if the, cartilage is still attached to the bone. Pain and recurrent swelling are related to activity. There may be localized tenderness at the site of the lesion. If the cartilage has separated from the underlying bone then it can cause severe pain. .If the loose fragment becomes entrapped within the joint space then the joint can get locked.

Causes
It occurs in the 10 20 age group. Trauma can be an etiologic factor. It is speculated that repeated trauma can lead to this condition.The impingement of the tibial spines on the lateral aspect of the femoral condyle may be contributory.There is a vasular insult to the femoral condyle.

A pain x-ray may show the lesion. Special views called tunnel views are sometimes needed to identify the crater. If the cartilage has not separated from the underlying bone then a MRI scan is necessary.

Treatment-
The treatment depends upon the intactness or otherwise of the overlying cartilage. This is best judged arthroscopically. In young patients,with intact cartilage, the lesion can be left alone till skeletal maturity as byt the time of fusion of the lower femoral epiphysis the lesion heals. If the cartilage is in the process of separating then it may be necessary to fix the fragment by wires or screws. If the fragment has separated then it is best to excise it. This leaves a problem of a crater in the midst of healthy cartilage. The operations of mosaicplasty where plugs of bone and cartilage are harvested from another part of the knee and implanted is very useful.
Another possibility is Autologous cartilage cell transplant. In this procedure, cartilage cells taken from the patient’s knee are cultured in a medium and reinjected into the knee after a gap of three weeks.

I do these procedures in Chennai. e mail me at drvenkat@kneeindia.com.