A case of OCD in a 15-year-old boy. Cross-section at the level of the medial femoral condyle (MFC); arrow—break in the subchondral bone at the edge of the OCD lesion; arrowheads—subchondral bone in the OCD zone; asterisks—swollen cartilage in the OCD zone; empty stars—cartilage covering the healthy part of the MFC, also with symptoms of slight swelling (increased echogenicity and slightly increased thickness); PAT—patella. Linear probe 7–18 MHz.