Snapshot A 13-year-old boy presents with left knee pain. He reports that he cannot specifically localize where the pain is in the left knee but has noticed it has progressively worsened over the course of 7 months. He also says that knee swelling typically appears after he plays basketball. On physical exam, there is mild swelling on the left knee. With the left knee in the flexed position with pressure over the medial femoral condyle, there is tenderness to palpation. Range of motion of the knee is intact. An anterior-posterior radiograph of the affected knee demonstrates crescent-shaped radiolucency surrounding subchondral bony fragments. Introduction Clinical definition login to view 1 more bullet Epidemiology login to view 10 more bullets Etiology login to view 3 more bullets Pathogenesis login to view 6 more bullets Prognosis login to view 2 more bullets Presentation Symptoms login to view 4 more bullets Physical exam login to view 3 more bullets Imaging Radiography login to view 5 more bullets Studies Diagnostic criteria login to view 1 more bullet Differential Avascular necrosis Treatment Conservative login to view 3 more bullets Operative login to view 4 more bullets Complications May progress to osteoarthritis of the affected joint