Osteochondritis dissecans (OCD) is a problem that commonly affects the knee. OCD mostly affects the femoral condyles of the knee. The femoral condyle is the rounded end of the lower thighbone, or femur. Each knee has two femoral condyles, the medial femoral condyle (on the inside of the knee) and the lateral femoral condyle (on the outside). Like most joint surfaces, the femoral condyles are covered in articular cartilage. Articular cartilage is a smooth, rubbery covering that allows the bones of a joint to slide smoothly against one another.
The problem occurs where the cartilage of the knee attaches to the bone underneath. The area of bone just under the cartilage surface is injured, leading to damage to the blood vessels of the bone. Without blood flow, the area of damaged bone actually dies. This area of dead bone can often be seen on an X-ray. The lesions usually occur in the part of the joint that holds most of the body’s weight. This means that the problem area is under constant stress and doesn’t get time to heal. It also means that the lesions cause pain and problems when walking and putting weight on the knee. It is more common for the lesions to occur on the medial femoral condyle, because the inside of the knee bears more weight. Children as young as nine or ten can develop this condition. The disease behaves differently in children and for this reason is given a separate name, juvenile osteochondritis dissecans (JOCD).
OCD and JOCD cause the same kind of damage to the knee, but they are separate diseases. In the child who is still growing the problem is much more likely to heal itself. In the adult, the bones are not growing and are less likely to heal spontaneously. For this reason the treatment and prognosis of OCD and JOCD can be very different.
It is thought that JOCD may be caused by repeated stress to the bone. Young people with JOCD have often been involved in competitive sports. A heavy schedule of training and competing can stress the femur in a way that leads to JOCD. There can be other causes.
OCD can occur any time from early adulthood on but most patients are adults under age 50. The cases of OCD that are first diagnosed in early adulthood probably began as JOCD. When a person gets OCD later in life it is probably a new problem. The cause of OCD are not fully understood. There is less of a link between strenuous, repetitive use and OCD. There are other risk factors such as steroid use but many people who develop OCD don’t have any particular risk factors. Because OCD leads to damage to the surface of the joint the condition can lead to problems with bone degeneration and osteoarthritis.
OCD and JOCD cause the same symptoms. The symptoms start out mild and grow worse with time. Both problems usually start with a mild aching pain aggravated by activity. It may become swollen and tender. Eventually, there is too much pain to put full weight on that knee. These symptoms are fairly common in athletes and may also be related to other conditions such as sprains, strains, and other knee problems.
As the condition becomes worse, the area of bone that is affected may collapse. The cartilage over this dead section of bone (the lesion) may become damaged. This can cause a snapping or catching feeling as the knee joint moves across the damaged area. In some cases the dead area of bone may actually become detached from the rest of the femur, forming what is called a loose body. This loose body may float around inside of the knee joint. The knee may catch or lock if the loose body gets in the way.
Your doctor take a full medical history and you will be asked about your current symptoms and about other knee or joint problems you have had in the past. Your doctor will then examine the painful knee.Your doctor will probably order an X-ray of your knee. Most OCD lesions will show up on an X-ray of the knee. If not, yourdoctor may suggest an MRI scan.
Many cases of JOCD can be completely healed with careful management. OCD may not ever completely heal but it can be treated. There are two methods of treating JOCD, nonsurgical treatment and surgery. Surgery is usually the only effective treatment for OCD.
Nonsurgical treatments help in about half the cases of JOCD. The goal is to help the lesions heal before growth stops in the thighbone.. Nonsurgical treatment of JOCD can take from 10 to 18 months. During that time, it is crucial to stop doing everything that causes pain to the knee. This means stopping exercise and sports. It may require using crutches or wearing a cast for a couple of months. As knee symptoms ease, exercises can be started that don’t involve placing weight through your foot. The exercises should be done carefully and should not cause any pain. Patients often work with physiotherapists.
Repeat MRI scans may be taken over the course of treatment to track how well the lesions are healing and to see if surgery is eventually needed. Even in JOCD, surgery may eventually be required. When the lesion has become so bad that it detaches totally or partially from the bone, nonsurgical treatment will not work.
If the lesion becomes totally or partially detached surgery is needed to remove the loose body or to fix it in place. In some cases your surgeon will be able to use the arthroscope to do the surgery (keyhole surgery).
Open surgery is needed when your surgeon can’t get a picture of the entire lesion, when it is unclear how the fragment would best fit into the bone, or when it would be too difficult to replace the fragment using the arthroscope. Open surgery usually requires larger incisions than arthroscopic surgery to allow the surgeon to see into the knee and perform the operation.
If the loose bone fragment is in a weight-bearing area of your bone, your surgeon will try to reattach it if at all possible. Your surgeon may use tiny metal pins or screws to hold the fragment in place. This sometimes proves difficult. The damaged fragment often doesn’t fit perfectly into the bone anymore.
Despite the difficulties, reattaching the fragment generally results in much better knee function than removing it. Your knee will not be as good as new, but a careful plan of exercise and follow-up care can help you use your knee again without pain.
If it is necessary to remove the fragment of bone and cartilage there are a number of other techniques which can be used to rebuild the damaged area. These techniques include the microfracture procedure, osteochondral grafting and autologous chondrocyte implantation where the patients own cartilage cells are grown in the lab and subsequently reimplanted into the defect.
Appropriate rehabilitation following either surgical or non surgical management is extremely important and will often be supervised by a physiotherapist.