Avascular Necrosis (AVN) is a disease resulting from temporary or permanent loss of blood supply. It frequently affects the femoral head and in this area, if left untreated, routinely causes premature joint destruction. In the USA, 5 to 10 per cent of cases of hip osteoarthritis requiring total hip replacement are primarily caused by AVN. In 33 to 72 per cent of patients, the disease is bilateral. The peak incidence is between 30 and 60 years of age, and the social costs of this pathology are remarkable. There is therefore increasing interest in hip joint preserving techniques such as conservative treatment through electromagnetic fields and shockwaves as well as joint preserving surgical techniques. This volume aims to present a complete overview of the current knowledge on AVN including therapeutic options.