Transient Hip Osteoporosis: Etiopathogenetic, Clinical, and Imaging Approach.

Transient Hip Osteoporosis (THO) is a relatively rare, benign, and usually self-limiting disease caused by bone marrow edema, depicted on MRI. It presents with sudden onset of pain or may be asymptomatic. Given the poor coverage of this subject in the relevant international literature and the lack of sufficient understanding of the aetiopathogenic mechanisms underlying this condition, no established diagnostic guidelines are available, leading to frequent under- or overdiagnosis. Therefore, great care should be taken to provide a correct differential diagnosis in order to achieve proper treatment. The international literature from 1990 to 2020 was searched in the PubMed and Google Scholar databases. The keywords: bone marrow edema, transient osteoporosis, osteonecrosis, and aetiopathogenesis were used, and original studies and review articles in English and Greek language were retrieved. Based on evidence provided in the current literature, this article offers a definition and describes in a concise and comprehensive manner the aetiopathogenesis, symptomatology, imaging findings, and differential diagnosis of the disease, in order to provide physicians with a sound knowledge of the condition, necessary to their clinical practice.