An osteochondral injury is an injury to the smooth surface on the end of bones, called articular cartilage (chondro), and the bone (osteo) underneath it. The degree of injury ranges from a small crack to a piece of the bone breaking off inside the joint. These fragments can be of many sizes and depths and can stay attached (stable) to the area that was injured or become loose (unstable) inside the joint. This injury is more common in adolescents and young adults and typically occurs at the knee, ankle or elbow. The causes of osteochondral injuries are not yet completely understood, but some theories are lack of blood supply to the affected area, heredity, direct compressive trauma or repetitive strain. Symptoms are: Pain with weight bearing activities, Swelling, Instability of the joint, Occasional catching and locking of the joint, Tenderness to touch over injured area,Decreased motion