Osteochondritis dissecans (OCD) is a disease of unknown etiology, characterized by separation of necrotic bone from its bony bed. While the juvenile form seen in patients with open physes has a 60-90% rate of spontaneous resolution, the adult form has virtually no chance of spontaneous healing. Plain X-rays are sufficient for the diagnosis, and magnetic resonance imaging (MRI) is essential for evaluation of disease progression and/or healing. The clinical correlation of MRI criteria defined in recent years to determine stability of the lesion is high. Juvenile OCD can be treated conservatively if there are no signs of instability on magnetic resonance images. Adult patients or unstable lesions in children should be treated surgically. For stable lesions, arthroscopic antegrade perforation is indicated to increase vascularity and stimulate healing. Unstable or displaced lesions should be treated with debridement, internal fixation, and cancellous bone grafting. Although cannulated metal screws are the most widely used implants for internal fixation, biodegradable implants have also been utilized in recent years. Loose fragments that are too deformed to be internally fixed should be removed and cartilage reconstruction techniques should be employed for the remaining crater. Long-term results of loose body removal alone are unsatisfactory. Modern cartilage restoration techniques are technically demanding due to the large, deep, and unconfined nature of the defect in the femoral condyle.