A portion or fragment of articular cartilage detaches in full or partially from subchondral bone avascular necrosis by lodging in joint.
Commonly due to trauma. Most commonly ankle joint (dorsal surface of talus). Pain is present in joint. On x-ray may see dense appearance and a radiolucent line of demarcation surrounding the fragment.
Treat conservatively if fragment still attached compression and rest.
Surgical - if fragment loose or conservative treatment fails.