Hip dysplasia is the medical term for instability, or looseness, of the hip joint that affects thousands of children each year. This ranges from mild instability to complete dislocation. Approximately one out of every 20 full-term babies has some hip instability and two to three per 1000 will require treatment.
Persistent hip instability is a silent childhood condition that frequently causes disability and arthritis in adults. In spite of the frequency and the potential for lifelong disability, there is poor awareness of this condition outside the medical profession. Early diagnosis and simple treatment is the best solution, but some cases are undetected or difficult to treat with current methods of care. Also, many children around the world do not have access to early diagnosis and treatment.
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Doctors use a number of different terms for hip dysplasia depending on severity and time of occurrence. These names include:
The term Developmental Dysplasia, or DDH, is generally preferred for infants because this condition can develop after birth. Also, the term congenital tends to refer to a defect where something is missing or added to normal tissues. In the case of DDH, the infant’s joint is otherwise normal except for the instability.
When the hip is completely out of the joint, it is called a dislocation. The hip is a ball-and-socket joint that is held together by ligaments. The ball is called the head of the femur (femoral head) and the socket is called the acetabulum.
In some infants the ligaments around the hip joint are loose and the ball does not stay in the socket. Sometimes the condition is mild and resolves spontaneously. Other times the ball is slightly or completely dislocated from the socket.
Hip dysplasia and dislocation are usually diagnosed by routine examination of the infant.
A “hip click” can be a sign of hip dislocation, but this can also be a normal finding in some infants because there are inside the hip joint that can make a snapping noise positions. But even with careful examination, complete hip dislocation can be difficult to detect in newborn infants. Also, there are documented cases where the hips were normal at birth, but became dislocated in the first few months of life. This is why it is important for babies to have regular examinations of the hips during the first year of life. An ultrasound study in young infants or X-ray study in older infants and children is performed when hip dysplasia is suspected. This is necessary to make the diagnosis or to be sure the hip is normal.