Infant & Child

Understanding Hip Dysplasia


Infant & Child

Developmental Dysplasia of the Hip (DDH)

What is Hip Dysplasia?

Hip dysplasia is often referred to as Developmental Dysplasia of the Hip or DDH and is generally the preferred term for babies and children with hip dysplasia since this condition can develop after birth. DDH is a medical term for general instability, or looseness, of the hip joint. Doctors use a number of different terms for hip dysplasia depending on severity and time of occurrence. These names include:

  • Hip Dysplasia
  • Developmental Dislocation of the Hip (DDH)
  • Hip Dislocation
  • Developmental Dysplasia of the Hip (DDH)
  • Acetabular Dysplasia
  • Congenital Dislocation of the Hip (CDH)

The term Congenital Dislocation of the Hip (CDH) tends to refer to a defect where something is missing or added to normal tissues. In the case of DDH, the infant/child’s joint is otherwise normal except for the instability.

How Common is Hip Dysplasia or DDH in Babies?

1 in 10

infants are born with hip instability.

1 in 100

infants are treated for hip dysplasia.

1 in 500

infants are born with completely dislocated hips.

Hip instability is the most common newborn abnormality.

  • Approximately 1 in 10 newborn infants has hip instability. That means the hips can be wiggled in the socket because of loose ligaments. Ninety percent tighten up naturally after birth.
  • Approximately 1 in 100 infants will need treatment for DDH
  • Approximately 1 in 500 infants has a completely dislocated hip
  • A very small number of hips dislocate after the first few weeks for unknown reasons

Hip Joint Anatomy

Hip Joint anatomy

The hip is a “ball-and-socket” joint that is held together by ligaments.

The ball is called the “femoral [fem-er-uhl] head” which is the top of the femur or thigh bone.

The socket is called the “acetabulum” [as-i-tab-yuh-luhm] and is a part of the pelvis.

The femoral head fits into the acetabulum creating the hip joint. This joint is normally held tightly in place by the surrounding ligaments and joint capsule.

Severity of Infantile Developmental
Dysplasia of the Hip (DDH)

Types of hip dysplasia

Hip dysplasia has a wide range of severity. In some children, the ligaments around the hip joint are loose allowing the hip to subluxate. This is when the ball is no longer centered in the socket. Other times the ball is slightly or completely dislocated from the socket.