Osteochondritis Dissecans (OCD)

This is a problem caused by a segment of bone losing its blood supply and in usually occurs in young people. It may present as knee pain or swelling or locking.
Diagnosis is by xray and the defect can be carefuuly evaluated by CT scans with 3D reconstruction.
Sometimes with rest the defect will heal but it often requires surgery involving pinning the loose piece of bone back in place and promoting a restoration of blood supply to the fragment, or removing it completely.