The hip joint is a ball-and-socket joint. The ball (femoral head) is at the top of the thigh bone (femur) and the socket (acetabulum) is part of the hipbone.
Legg-Calve-Perthes (LEG-kahl-VAY-PER-tuz) disease is a childhood condition that occurs when blood supply to the ball part (femoral head) of the hip joint is temporarily interrupted and the bone begins to die.
This weakened bone gradually breaks apart and can lose its round shape. The body eventually restores blood supply to the ball, and the ball heals. But if the ball is no longer round after it heals, it can cause pain and stiffness. The complete process of bone death, fracture and renewal can take several years.
To keep the ball part of the joint as round as possible, doctors use a variety of treatments that keep it snug in the socket portion of the joint. The socket acts as a mold for the fragmented femoral head as it heals.
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Signs and symptoms of Legg-Calve-Perthes disease include:
- Pain or stiffness in the hip, groin, thigh or knee
- Limited range of motion of the hip joint
- Pain that worsens with activity and improves with rest
Legg-Calve-Perthes disease usually involves just one hip. Both hips are affected in some children, usually at different times.
When to see a doctor
Make an appointment with your doctor if your child begins limping or complains of hip, groin or knee pain. If your child has a fever or can't bear weight on the leg, seek emergency medical care.
Legg-Calve-Perthes disease occurs when too little blood is supplied to the ball portion of the hip joint (femoral head). Without enough blood, this bone becomes weak and fractures easily. The cause of the temporary reduction in blood flow to the femoral head remains unknown.
Risk factors for Legg-Calve-Perthes disease include:
- Age. Although Legg-Calve-Perthes disease can affect children of nearly any age, it most commonly begins between ages 4 and 10.
- Your child's sex. Legg-Calve-Perthes is about four times more common in boys than in girls.
- Race. White children are more likely to develop the disorder than are black children.
- Genetic mutations. For a small number of people, Legg-Calve-Perthes disease appears to be linked to mutations in certain genes, but more study is needed.
Children who have had Legg-Calve-Perthes disease are at higher risk of developing hip arthritis in adulthood — particularly if the hip joint heals in an abnormal shape. If the hipbones don't fit together well after healing, the joint can wear out early.
In general, children who are diagnosed with Legg-Calve-Perthes after age 6 are more likely to develop hip problems later in life. The younger the child is at the time of diagnosis, the better the chances for the hip joint to heal in a normal, round shape.