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News Letter

Osteochondritis Dissecans of the Knee Print E-mail

Introduction

Osteochondritis dissecans (OCD) is a problem that affects the knee. The disease behaves much differently in children and for this reason is given a separate name, juvenile osteochondritis dissecans (JOCD). The condition affects the end of the big bone of the thigh commonly known as the femur.

These disorders are uncommon and most often occur in young athletes. Children as young as nine or ten years old can develop JOCD. Any adult can develop OCD, with most patients ranging in age from early adulthood to age fifty.

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. For this reason, the treatment and recovery after OCD and JOCD can be very different.

A joint surface damaged by OCD doesn't heal naturally. Even with surgery, OCD usually leads to future joint problems, including degenerative arthritis and osteoarthritis.

Anatomy

Most cases of OCD and JOCD affect the femoral condyles of the knee. The femoral condyle is the part of the knee made up of the rounded end of the 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, slick 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 be seen on an X-ray and is sometimes referred to as the osteochondritis lesion.

OCD and JOCD usually affect the part of the joint holding most of the body's weight. The lesions are under constant stress and don't get time to heal. Also, 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.

Causes


JOCD

Many doctors think that JOCD is caused by repeated stress to the bone. Most young people with JOCD have been involved in competitive sports since they were very young. A heavy schedule of training and competing can stress the femur in a way that leads to JOCD. In some cases, other muscle or bone problems can cause extra stress and contribute to JOCD.

OCD

Sometimes JOCD is not treated or does not heal completely. When this happens, JOCD develops into OCD. OCD can occur any time from early adulthood on, but most patients are adults under age fifty. Cases of OCD first diagnosed in early adulthood probably began as JOCD. When a person gets OCD later in life, it is probably a new problem.

Doctors aren't sure what causes OCD. There is less of a link between strenuous repetitive use and OCD. 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. The damage to the joint surface affects the way the joint works. Over time this imbalance can lead to abnormal wear and tear on the joint and can cause degenerative arthritis and osteoarthritis.

Symptoms

OCD and JOCD cause the same symptoms usually starting out mild and growing worse with time. Both problems usually start with a mild aching pain. Moving the knee becomes painful, and it may be swollen and sore to the touch. Eventually, there is too much pain to put full weight on that knee. These symptoms are fairly common in athletes. They are similar to the symptoms of sprains, strains, and other knee problems.

As the condition becomes worse, the area of bone that is affected may collapse causing a notch to form in the smooth joint surface. 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 notched 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 when moved if the loose body gets in the way.

Diagnosis

History and Physical Exam

Your doctor will ask many questions about your medical history. 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 by feeling it and moving it. You may be asked to walk, move, or stretch your knee. This may hurt, but it is important that your doctor knows exactly where and when your knee hurts.

Radiological Tests

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, your doctor may suggest a bone scan. A bone scan is the best way to see the lesions in the very early stages.

A bone scan involves injecting a special type of dye into the blood stream and then taking pictures of the bones with a special camera. This camera is similar to a Geiger counter and can pick up very small amounts of radiation. The injected dye is a very weak radioactive chemical. It attaches itself to areas of bone that are undergoing rapid changes--such as a healing fracture. The camera provides a picture that is used by your doctor to see OCD lesions in the very early stages.

Your doctor may want to do other imaging tests, such as magnetic resonance imaging (MRI). The MRI machine uses magnetic waves rather than X-rays to show the soft tissues of the body. With this machine, doctors are able to create pictures that look like slices of the knee and see the anatomy, and any injuries, very clearly. These tests may help determine the extent of damage from OCD and JOCD, and they also help rule out other problems.

Treatment

Many cases of JOCD can be completely healed with careful treatment. OCD will probably never completely heal, but it can be treated. There are two methods of treating JOCD: conservative treatment to help the lesions heal, and surgery. Surgery is usually the only effective treatment for OCD.

Nonsurgical Treatment

Conservative treatments help in about half the cases of JOCD. The goal is to help the lesions heal before growth stops in the thighbone. Even if imaging tests show that growth has already stopped, it is usually worth trying conservative treatment. When conservative treatment works, the knee seems as good as new, and the JOCD doesn't seem to lead to arthritis.

Conservative treatment of JOCD can take from ten to eighteen months. During that time, it is crucial to stop activities that cause pain to the knee. This means stopping exercise and sports. It may require using crutches or wearing a cast for a couple of months when the knee is symptomatic. As the knee becomes less symptomatic, non-weight-bearing exercise can be started. The exercises should be done carefully and should not cause any pain. Patients often work with physical therapists to develop an exercise program.

Regular bone scans will be taken throughout the 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, conservative treatment will not work. Even with treatment, some patients continue to have symptoms or their bone scans show signs that the damage is getting worse.

Some patients who are too near the end of bone growth may not benefit with conservative treatment. When these problems develop, your surgeon may suggest surgery.

Surgery

If the lesion becomes totally or partially detached, surgery is needed to remove the loose body or to fix it in place. Your doctor will need to gather information about your knee and your problem before surgery. This may require additional bone scans, X-rays, or MRIs. Your doctor may also use an arthroscope, a tiny camera inserted into the knee, to look at your knee before surgery.

These tests are important because your doctor needs to know the exact location and the size of the lesion to determine what kind of surgery will work best. In some cases, your doctor will be able to use the arthroscope to do the surgery. If the arthroscope can be used, the procedure requires smaller incisions than for an open surgery, which may reduce the time needed before the knee can be moved and exercised.

Open surgery is needed when your doctor 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 doctor will try to reattach it if at all possible. Your doctor 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. And the bone around the fragment may have changed requiring your doctor to rebuild it.

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.

In rare cases, the lesion must be removed from a weight-bearing area. Your doctor may try to fill in the hole using an allograft. An allograft is an actual transplant of bone and cartilage from a donor into your knee. The bone is usually obtained from a bone and tissue bank.

In this case, bone material is transplanted into the hole left in the bone. Allografts have risks, including graft rejection and infection. But they can be very successful in returning function to the knee.

Rehabilitation

If you have surgery, your doctor may have you use a continuous passive motion (CPM) machine afterwards to help the knee begin to move and to alleviate joint stiffness. A CPM machine gently moves your joint for you.

With the exception of arthroscopic removal of a loose body, patients are instructed to avoid putting too much weight on their foot when standing or walking for up to six weeks. This gives the area time to heal. Weight bearing is usually restricted for up to four months after an allograft.

Patients are strongly advised to follow the recommendations about how much weight is safe. They may require a walker or pair of crutches for up to six weeks to avoid putting too much pressure on the joint when they are up and about.

Many doctors will have their patients take part in formal physical therapy after knee surgery for osteochondritis lesions. The first few physical therapy treatments are designed to help control the pain and swelling from the surgery. Physical therapists will also work with patients to make sure they are only putting a safe amount of weight on the affected leg.

Exercises are chosen to help improve knee motion and to get the muscles toned and active again. At first, emphasis is placed on exercising the knee in positions and movements that don't strain the healing part of the cartilage. As the program evolves, more challenging exercises are chosen to safely advance the knee's strength and function.

Ideally, patients will be able to resume their previous lifestyle activities. Some patients may be encouraged to modify their activity choices, especially if an allograft was used.

The therapist's goal is to help patients keep their pain under control, ensure safe weight bearing, and improve their strength and range of motion. When patients are well underway, regular visits to the therapist's office will end. The therapist will continue to be a resource, but patients will be in charge of doing their exercises as part of an ongoing home program.

 

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