Generalities:

Osteochondritis dissecans is a joint disease in which the bone beneath the cartilage of a joint dies due to a lack of blood flow. This bone and cartilage can break away, causing pain and possibly making it difficult to move the joint.
Osteochondritis dissecans occurs most frequently in children and adolescents. It can cause symptoms either after a joint injury or after several months of activity, especially from high-impact activities such as jumping and running, which affect the joint. This disease is most commonly seen in the knee, but it also occurs in the elbows, ankles, and other joints.