Osteochondritis dissecans (OCD) is a condition that develops in joints, most often in the knee, ankle, and elbow (although it can also occur in other joints). OCD more often affects children and adolescents. It occurs when a small segment of the bone begins to separate from its surrounding region. This is due to a lack of blood supply. As a result, the small piece of bone and the cartilage covering it begin to loosen and crack.
In many cases of OCD in children, the affected bone and cartilage heal on their own. In grown children and young adults, OCD can have more serious effects such as the lesions having a greater chance of separating from the surrounding bone and cartilage, and can even detach and float around inside the joint. In these cases, surgery may be necessary.