Since its introduction into clinical use, magnetic resonance imaging (MRI) has become well established in the diagnosis of injuries of the knee joint and has replaced diagnostic arthroscopy as the primary evaluation method. Traumatic lesions of the ligaments, menisci, and articular surfaces are common injuries that can be confidently detected using MRI. This article reviews the basic principles of the examination technique of the knee, the normal MRI anatomy of the internal joint structures, and the typical findings in injuries of the cruciate ligaments, collateral ligaments, and mensci, in traumatic dislocation of the patella, and in acute osteochondral lesions.