Osteochondritis dissecans (OCD) is a condition that affects body joints where a piece of cartilage (a tough elastic tissue) or bone loosens from the affected bone due to lack of blood supply. The resulting piece of bone or cartilage may stay in place or fall into the joint space, making the joint unstable. "Osteo" refers to "bone" and "chondritis" is inflammation of the cartilage. Dissecans refers to a condition where cartilage, along with a thin layer of the bone beneath it, comes loose from the end of a bone, causing damage to the overlying cartilage of the joint. The most commonly affected joints are the knee, ankle, and elbow.

Sometimes, loose pieces of cartilage and bone may stay close to where they detached, so the symptoms of OCD may be less pronounced. In other cases, the cartilage and bone can get trapped in the joint space, causing more severe symptoms such as weakness, sharp pain, and locking of the joint.

OCD is commonly seen in growing children and middle-aged people, and those active in sports that involve running and jumping, such as gymnastics, or pitching, such as baseball. A majority of the affected patients are between the ages of 10 and 40. Men are twice as likely to develop OCD as women. In adults, OCD is defined as occurring in mature bone, while juvenile OCD is when the condition happens in the growing bones of children.

While the exact cause of OCD is unknown, up to 40 percent of OCD cases are thought to develop as a result of repetitive trauma. Repetitive injury to a body part that goes unrecognized over a period of time can result in reduction of blood flow to the end of the affected bone (ischemia), leading to OCD. Other factors include:

• Genetic predisposition

• Fat emboli (blocking of an artery due to fat)

• Thrombosis (blood clot in a blood vessel)

• Infection

Any factor that leads to death of a localized area of bone can result in bone breakdown (osteonecrosis), which can lead to OCD.

Under certain conditions, OCD can heal on its own. If the loosened piece of cartilage and bone stays put, lying close to where it detached, there may be few or no symptoms of OCD, and the fracture can often heal by itself.

However, if the condition does not resolve on its own, cartilage from the affected bone breaks loose, causing weakness of the affected joint along with sharp pain, swelling, and tenderness. There may be locking or popping of the joint and decreased range of motion. Physical activity can trigger pain, and the joint can get locked due to loose fragments getting caught between bones. Sensations of the joint "giving way" and an inability to bear weight are common signs of OCD.

Persistent symptoms, especially pain or soreness in the most commonly affected joints, are clues that certain tests by a doctor must be carried out. Normally, an X-ray, MRI (magnetic resonance imaging), or a CT (computerized tomography) is done to confirm whether the loose cartilage or bone is stable or has moved into the joint space. 

When an X-ray of one joint reveals OCD, an X-ray of the other joint will also be taken for comparison. An MRI can determine whether surgery or more conservative treatment is required, while a CT scan can show the exact location of the loose fragments within the joint.

The recommended treatment depends on the patient's age and the stability of the fragments. In younger patients whose bones are still growing, the symptoms are usually mild and can be treated with rest and decreased physical activity. Physical therapy in the form of stretching exercises can strengthen the muscles that support the involved joint. 

Swimming is another therapy that may be advised. Nonsteroidal anti-inflammatory medications (NSAIDs) to reduce pain and inflammation may also help.

In adults, where the bones are mature, surgical intervention might be necessary to remove the loose fragments or reattach them to the bone.

The outcome is more favorable for young people, who can typically return to their usual activities after a rest period of around eight weeks. The goal is to protect the injured cartilage area while learning to strengthen the muscles of the joint. Surgery may not be necessary for younger patients who are not experiencing much pain. With rest and a period of non-weight bearing, the bony fragment in young patients may heal on its own into its anatomic location. 

In adults, when surgery is performed, there is a greater chance of chronic pain, functional impairment, and development of osteoarthritis. Here, the goal is to keep pain under control and get muscles toned and active again. 

Whether or not hereditary factors are involved, anyone can develop an OCD or cartilage injury. Adolescents active in sports will benefit from being educated about this condition because they are more susceptible, especially if their sport involves running and jumping. Practicing the correct techniques and learning the proper mechanisms of the sport can help avoid or reduce injury.

More research is needed to completely understand OCD, but what is known is that early diagnosis and appropriate management can help prevent long-term complications and allow active people to lead healthy sporting lives.