Complex sentence: Osteochondritis dissecans (sometimes spelled "dessecans", and abbreviated "OCD") is a painful condition within a joint of the body in humans or animals, in which fragments of cartilage or bone have become loose within a joint, leading to pain and inflammation.
Split into simpler sentences: Osteochondritis dissecans (sometimes spelled "dessecans", and abbreviated "OCD") is a painful condition within a joint of the body in humans or animals is inflamed. In osteochondritis, fragments of cartilage or bone have become loose within a joint, leading to pain and inflammation.