This terminology introduces challenges, because the joint in a newborn is formed from cartilage and is still malleable, making the onset difficult to ascertain. The newer term DDH also encompasses occult dysplasia (e.g. an underdeveloped joint) without dislocation and a dislocation developing after the "newborn" phase.The term is not used consistently. In pediatric/neonatal orthopedics it is used to describe unstable/dislocatable hips and poorly developed acetabula. For adults it describes hips showing abnormal femur head or acetabular x-rays.Some sources prefer the term "hip dysplasia" over DDH, considering it to be "simpler and more accurate", partly because of the redundancy created by the use of the terms developmental and dysplasia. Types of DDH include subluxation, dysplasia, and dislocation. The main types are the result of either laxity of the supporting capsule or an abnormal acetabulum. Imaging
Hip dysplasia diagnosed by ultrasound and projectional radiography ("X-ray"). Ultrasound imaging is generally preferred at up to 4 months due to limited ossification of the skeleton.Despite the widespread of ultrasound, pelvis X-ray is still frequently used to diagnose or monitor hip dysplasia or for assessing other congenital conditions or bone tumors. The most useful lines and angles that can be drawn in the pediatric pelvis assessing hip dysplasia are as follows: Different measurements are used in adults.
Cases of femoral nerve palsy and avascular necrosis of the femoral head have been reported with the use of the Pavlik harness, but whether these cases were due to improper application of the device or a complication encountered in the course of the disorder remains unresolved. Complications arise mainly because the sheet of the iliopsoas muscle pushes the circumflex artery against the neck of the femur and decreases blood flow to the femoral head, so the Frejka pillow is not indicated in all the forms of the developmental dysplasia of the hip. Other devices employed include the spica cast, particularly following surgical closed reduction, open reduction, or osteotomy in babies and young children. Traction is sometimes used in the weeks leading up to a surgery to help stretch ligaments in the hip joint, although its use is controversial and varies amongst physicians. Surgery
In older children  the adductor and iliopsoas muscles may have to be treated surgically because they adapt to the dislocated joint position (contracture). Braces and splints are often used following either of these methods to continue treatment. Although some children "outgrow" untreated mild hip dysplasia and some forms of untreated dysplasia cause little or no impairment of quality of life, studies have as yet been unable to find a method of predicting outcomes. On the other hand, it has often been documented that starting treatment late leads to complications and ends in poor results. Hip replacement and osteotomy
Hip dysplasia is often cited as causing osteoarthritis of the hip at a comparatively young age.