Osteochondritis dissecans


The Basics

  • Osteochondritis Dissecans is a condition where a chunk of bone and its overlying articular cartilage becomes partially or even completely detatched from the surface of the joint.
  • OCD occurs most frequently on the medial femoral condyle and most often in teenagers or young adults.
  • Nobody really fully understands what the exact cause of OCD might actually be.
  • The best imaging investigation for OCD is an MRI scan.
  • If the OCD is caught early and the lesion is not beginning to detach, then it can sometimes settle down with just rest and avoidance of exercise, particularly impact.
  • If an OCD lesion becomes partially detached then it can be possible to fix the fragment back in place surgically, via knee arthroscopy.
  • If an OCD lesion has completely detached and the fragment is floating around in the knee then it is more often than not too late by then to try and fix it back in place, and the fragment normally needs to be removed via knee arthroscopy. There are then various different surgical techniques that can be used for filling and resurfacing the defect that is left on the surface of the knee joint.



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Osteochondritis Dissecans (OCD) is a disorder that tends to occur in younger people (children and young adults). It is where a chunk of bone (osteo) plus the overlying articular cartilage (chondral) becomes partially or completely detached from the joint surface. The most common place for OCD to arise is on the surface of the medial femoral condyle.

Rather confusingly, when there is direct trauma to the surface of a joint and a chuck of bone and cartilage is actually knocked off leaving a hole in the joint surface, this is referred to as an osteochondral defect. However, the term ‘OCD’ is normally taken to refer specifically to ‘Osteochondritis Dissecans’ and not to ‘osteochondral defect’, even though if an OCD lesion does become completely detached from the joint surface and displaced, then the actual end-result will actually look pretty much identical to a traumatic osteochondral defect.

Nobody knows what the exact cause of Osteochondritis Dissecans definitely is. However, some people believe that it is caused by repetitive microtrauma, some feel that it is a microvascular disorder and some believe that it might even be autoimmune. Nearly all of the time, however, no specific cause can be indentified, and the actual disease process and consequences are the same anyway, regardless of whatever the underlying cause might have been.

In the early stages of OCD, there may just be bruising of the bone in a small area under the articular cartilage on the joint surface. If the disease progresses then a small island of bone can begin to become partially detached and the articular cartilage around the edge overlying this may begin to crack or split. If things deteriorate further then the osteochondral fragment might begin to partially detach, and eventually it may detach completely and displace, floating around the knee as a loose body. The resulting defect in the joint surface looks almost like something has taken a small bite out the surface of the bone.




Symptoms

The symptoms that might be caused by OCD depend largely on:-

  • which surface of the joint is affected (weight-bearing vs non-weight-bearing),
  • the size of the lesion
  • the stability (stage) of the lesion, and
  • whether or not the OCD fragment has actually detached and is loose.

The symptoms that OCD may cause can include:-

  • pain
  • swelling
  • clicking
  • catching
  • giving way
  • locking

The ‘mechanical-type’ symptoms (catching, giving way, locking) will be more likely if the OCD lesion is unstable or if it is detached and loose in the joint.




Treatment

Treatment of ODC depends on various factors, including the location of the defect and the stage of the disorder.

If the OCD lesion is in an early stage, then all that may be needed might be to advise rest and avoidance of heavy weights or impact, as some OCD lesions will actually just simply get better on their own with time, if the joint surface is protected.

If an OCD lesion is partially detached and unstable, then the best treatment is to try and fix it back in place surgically, by pinning the chunk of cartilage and bone firmly back in place, which normally works very well.

If an OCD lesion is actually completely displaced and loose in the joint, then occasionally it might still be possible to pin it back in place. However, normally the loose fragment will have been damaged whilst floating around in the joint, and more often that not it simply has to be removed from the knee. If the resultant defect is on a weight bearing surface then it is then likely to need further more complicated surgery, to pack the bone defect with bone graft and to cover the surface with an articular cartilage graft, which can be very difficult.



Written by Mr Ian McDermott
Consultant Knee Surgeon London
Last updated 24-5-12