When blood supply to the area at the end of your bone is cut off, a condition known as osteochondritis dissecans may develop. The affected bone and its covering of cartilage may stay in place and cause no symptoms. Or, a fragment may gradually loosen, separate and cause pain.

The knee is most commonly affected, although osteochondritis dissecans can occur in other joints, including your elbow, hip and ankle.

Most people diagnosed with symptomatic osteochondritis dissecans are older children, teenagers and young adults, particularly those active in sports.

Early diagnosis and treatment of osteochondritis dissecans are important to minimize your risk of long-term disability. If you're treated promptly, your chances of recovery and return to your usual activities, including participation in sports, are good.

Pain is the most common symptom of osteochondritis dissecans. The pain may be triggered by physical activity — for example, knee pain that occurs while walking up stairs, climbing a hill or playing sports.

Signs and symptoms of osteochondritis dissecans include:

• Pain
• A "locking" of your joint — the joint "sticks" and won't move through its full range of motion
• A feeling that your joint is "giving way" or weakening
• Decreased joint movement — an inability to straighten your leg or arm fully, or a limited range of motion
• Limping
• Swelling and tenderness of the skin over your joint
• Stiffness after resting

Doctors are unsure of the cause of osteochondritis dissecans. However, a number of factors may contribute to the disorder:

• Injury or stress. High on the list is repetitive force (trauma or stress) to the affected joint, particularly if you're very active. You may experience small, multiple episodes of minor unrecognized injury that, over time, cause a tiny fracture that damages the overlying cartilage of a joint.
• Restricted blood supply. An impaired blood supply to your bone (vascular insufficiency) also may play a role in the condition. The impaired supply is due to a slight blockage of a small artery and gradually can cause a breaking down or death of bone tissue (avascular necrosis).
• Your genetic makeup. Some people also may be genetically predisposed to develop osteochondritis dissecans.

Regular physical activity — particularly when it involves repetitive impact movement, such as jumping — may put stress on your joints and place you at increased risk of osteochondritis dissecans.

Young people between 10 and 20 — especially active ones involved in organized sports that involve jumping, cutting or pivoting, such as tennis, gymnastics, basketball and wrestling — tend to be most affected by symptomatic osteochondritis dissecans. People involved in throwing sports, such as baseball pitchers, may be vulnerable as well.

Although osteochondritis dissecans is rare, it's becoming more commonly diagnosed, particularly among young females, as their participation in organized sports increases.

If you have persistent pain or soreness in your knee, elbow or another joint, see your doctor. Other signs and symptoms that should prompt a call or visit to your doctor include joint swelling or an inability to fully extend an extremity.

If you know that you've recently suffered a joint injury — or feel a worsening of pain during physical activity — this could be a further indication of possible osteochondritis dissecans. Seek medical attention.

To make the diagnosis of osteochondritis dissecans, your doctor begins by taking a thorough medical history — asking about your symptoms, including pain, and whether you've had joint problems in the past.

Your doctor will ask about whether you've experienced an injury to the affected joint and when it occurred. In addition, your doctor will ask about your exercise routines, whether they involve any throwing movements (if the pain is in your elbow), and whether the discomfort has increased in recent weeks and months.

Then your doctor will likely conduct a physical examination, checking the stability of the joint and whether there is a clicking or locking when you move the joint.

Imaging tests
Your doctor may ask you to undergo one or more imaging procedures to help diagnose and determine the severity of the disorder. X-rays of your joint from various angles could show abnormalities in the surface of your joint. Your doctor may recommend that both joints be X-rayed (both the right and left knee, for example) to compare them.

Although the diagnosis can often be made with X-rays alone, X-rays cannot show breaks or cracks in the cartilage, nor the stability of the joint. Other imaging techniques may be used to analyze the cartilage and provide other information to help make the diagnosis:

• Computerized tomography (CT) provides computer-enhanced images of the joint structures. It can also detect any bone and cartilage fragments and pinpoint their location, including whether they have settled in the joint space.
• Magnetic resonance imaging (MRI) uses magnetic fields to create detailed pictures of your joint, which will provide information about its structure, the accumulation of fluid in the area and the visualization of loose fragments. Doctors frequently use MRI to help decide whether healing will occur with conservative treatment or whether surgery is necessary.
• Bone scans involve injecting dye into your bloodstream, and then taking images of your bones.

If you don't receive effective treatment for osteochondritis dissecans, it's possible that degenerative osteoarthritis will develop in the affected joint.

Treatment of osteochondritis dissecans is intended to restore the normal functioning of the affected joint and to relieve pain, as well as reduce the risk of osteoarthritis. No single treatment, however, is effective for everybody.

Conservative measures
Initially, your doctor will likely recommend conservative measures, which are effective in most cases. They may include:

• Resting your joint. Refrain from impact activities such as jumping and from cut-pivot activities in which you can put strain on your knee as you rotate the joint. If your injury is due to a throwing sport, you'll be instructed to refrain from throwing.
• Immobilizing your joint. This may involve using a hinged brace or crutches if your knee or ankle is affected.
• Using nonsteroidal anti-inflammatory medications. These include aspirin, ibuprofen (Advil, Motrin, others) and naproxen sodium (Aleve, Naprosyn).
• Avoiding competitive sports and intense physical activity. These activities may put a strain on your affected joint and cause pain. Resting for at least six to eight weeks and limiting competitive activity helps ease signs and symptoms for most people.
• Physical therapy. Most often, this therapy includes stretching and range-of-motion exercises, and strengthening exercises for the muscles that support the involved joint. Low-impact aerobic conditioning, such as use of a stationary bicycle, helps to maintain cardiovascular fitness.

When surgery is an option
Although most people see improvement with conservative measures, surgery is an option when problems persist for at least three months, the joint motion is blocked and other treatment options haven't helped.

Surgery called arthroscopy is minimally invasive. It begins when your surgeon inserts a thin scope into the joint space to visualize the area on a television monitor. The surgeon then determines the location of the damage and decides upon the best type of surgical procedure.

Tiny surgical instruments are inserted into small incisions, and loose bone fragments may be reattached or removed. When cartilage fragments are still attached to the bone, they can be tightly secured with pins or screws. The goal of this surgery is to restore normal blood flow and improve joint function.

Physical therapy after surgery is necessary to optimize strength, stability and function.

Although most people with osteochondritis dissecans are free of symptoms after appropriate treatment, doctors may recommend restrictions on daily activities to help reduce the risk of recurrence. For example, while young athletes may be able to return to playing sports, doctors may ask that they limit participation initially to light workouts, and then gradually work back into competition after completing sport-specific conditioning exercises.

Adolescents participating in organized sports may benefit from education on the risks to their joints associated with overuse. Learning the proper mechanics and techniques of their sport and participating in strength training and stability training exercises may help reduce the chance of injury.