Developmental dysplasia of the hip (DDH) is the most common musculoskeletal disorder of the infant age. Its incidence ranges from 0.06/1000 to 76.1/1000 live births and is more frequent in female infants. Breech position, family history and firstborn children are the main risk factors for DDH and this disorder is also associated with the presence of other congenital deformities. Anatomically, the acetabulum remains shallow and the femoral head grows in a wrong position. Clinical examination is important and tests such us Barlow and Ortolani give indications only for a part of the spectrum of this entity. Nowadays the sonographic examination is the most accurate option for the diagnosis. Graf classification categorizes the DDH cases in four types, from normal to dislocated hip, by description and measuring specific angles in sonographic examination. The wide usage of ultrasonography has decreased the non-diagnosed or neglected cases; treatment begins immediately in young age and is usually conservative with the usage of devices such as Pavlik harness and hip spica. To enhance the literature, we searched for published studies on DDH, to summarize the pathogenesis and the diagnosis and to discuss the treatment and outcome of the patients with this disorder.