Although the disease called avascular necrosis (AVN) was discovered in Egyptian mummies, there is a lack of information available in understanding and treating this pathology. AVN is a condition where cellular death of bone components occurs due to an interruption of the blood supply. Nusem discusses the morphopathological appearance of AVN. Avascular necrosis tends to affect young adults and often progresses despite appropriate treatment. Although some of the predisposing factors have been recognised, the pathogenesis of AVN remains unclear. Cheung discusses hypotheses and pathophysiologic mechanisms underlying the disease while Lloyd addresses new advances in the field of radiology. Most authors agree that successful treatment directly relates to the stage of the disease, which in most case is reflected by a specific classification system. Each chapter will provide an overview of the specific systems most commonly used for the anatomical region described therein. Various anatomical locations more commonly involved with AVN are discussed specifically. Nusem discusses a rare spinal disorder characterised as avascular necrosis of a vertebral body occurring in a delayed fashion after minor trauma (Kümmell's disease). The femoral head is most commonly affected by AVN; the clinical presentation and existing treatment options are discussed by Cowie and coauthors. AVN around the knee is presented by Myers and colleagues while AVN affecting the foot is presented by Nihal and coworkers. In the upper extremity AVN of the capitellum (Panner's disease) is presented by Shamimudeen while AVN of the lunate (Kienböck's disease) is discussed by Rhau and colleagues and AVN of the scaphoid (Preiser's disease) is described by Wong and his coworkers. Although AVN is not common in the paediatric age group, Jabur presents on AVN after slipped femoral capital epiphysis. Bone marrow oedema is a common finding in MRIs done in patients with AVN and Nusem will discuss bone marrow oedema syndrome and its differential diagnosis.