Femoroacetabular impingement is the entity describing abnormal contact of the femur and the acetabular rim which causes cartilage and labrum degeneration due to repetitive trauma leading to early osteoarthritis of the hip joints. Femoroacetabular impingement is regarded as an important reason of young adult hip pain. Femoroacetabular impingement first described by Ganz is classified as `cam`, `pincer` and mixed types. Its early diagnosis and treatment is important to prevent osteoarthritis. Radiological assessment is essential to evaluate hip morphology and so preoperative planning. Labral tears and cartilaginous damage can only be diagnosed by magnetic resonance imaging. In addition to morphological changes, bone marrow edema at abnormal contact regions, subchondral cysts and osteophytes can be detected by magnetic resonance imaging. Magnetic resonance arthrography raises the accuracy of diagnosis of the labral tears. Magnetic resonance imaging and magnetic resonance arthrography provide recognition of labral-cartilaginous damage and subchondral bone marrow edema in the early stage of degeneration and are useful in the postoperative assessment.