Hip dysplasia is the medical term for a hip socket that doesn't fully cover the ball portion of the upper thighbone. This allows the hip joint to become partially or completely dislocated. Most people with hip dysplasia are born with the condition.
Doctors will check your baby for signs of hip dysplasia shortly after birth and during well-baby visits. If hip dysplasia is diagnosed in early infancy, a soft brace can usually correct the problem.
Milder cases of hip dysplasia might not start causing symptoms until a person is a teenager or young adult. Hip dysplasia can damage the cartilage lining the joint, and it can also hurt the soft cartilage (labrum) that rims the socket portion of the hip joint. This is called a hip labral tear.
In older children and young adults, surgery may be needed to move the bones into the proper positions for smooth joint movement.
Signs and symptoms vary by age group. In infants, you might notice that one leg is longer than the other. Once a child begins walking, a limp may develop. During diaper changes, one hip may be less flexible than the other.
In teenagers and young adults, hip dysplasia can cause painful complications such as osteoarthritis or a hip labral tear. This may cause activity-related groin pain. In some cases, you might experience a sensation of instability in the hip.
At birth, the hip joint is made of soft cartilage that gradually hardens into bone. The ball and socket need to fit together well because they act as molds for each other. If the ball isn't seated firmly into the socket, the socket will not fully form around the ball and will become too shallow.
During the final month before birth, the space within the womb can become so crowded that the ball of the hip joint moves out of its proper position, which results in a shallower socket. Factors that may reduce the amount of space in the womb include:
- First pregnancy
- Large baby
- Breech presentation
Hip dysplasia tends to run in families and is more common in girls. The risk of hip dysplasia is also higher in babies born in the breech position or with foot deformities.
Later in life, hip dysplasia can damage the soft cartilage (labrum) that rims the socket portion of the hip joint. This is called a hip labral tear. Hip dysplasia also can make the joint more likely to develop osteoarthritis. This occurs because of higher contact pressures over a smaller surface of the socket. Over time, this wears away the smooth cartilage on the bones that helps them glide against each other as the joint moves.