<Tr> <Th> MeSH </Th> <Td> D010008 </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> Osteochondritis dissecans (OCD or OD) is a joint disorder in which cracks form in the articular cartilage and the underlying subchondral bone . OCD usually causes pain and swelling of the affected joint which catches and locks during movement . Physical examination typically reveals an effusion, tenderness, and a crackling sound with joint movement . </P> <P> OCD is caused by blood deprivation in the subchondral bone . This loss of blood flow causes the subchondral bone to die in a process called avascular necrosis . The bone is then reabsorbed by the body, leaving the articular cartilage it supported prone to damage . The result is fragmentation (dissection) of both cartilage and bone, and the free movement of these bone and cartilage fragments within the joint space, causing pain and further damage . OCD can be difficult to diagnose because these symptoms are found with other diseases . However, the disease can be confirmed by X-rays, computed tomography (CT) or magnetic resonance imaging (MRI) scans . </P>

What is an ocd lesion of the knee