Legg-Calve-Perthes disease is a childhood condition associated with a temporary loss of blood supply to part of the hip joint. Without adequate blood flow, a process can occur in which the bone becomes unstable, and may break easily and heal poorly.

Legg-Calve-Perthes disease typically affects one hip, but sometimes it develops in both hips. Although Legg-Calve-Perthes disease can affect children of nearly any age, it's most common among boys ages 4 to 8.

Children who develop Legg-Calve-Perthes disease when they're very young often have the best outcomes. The younger your child, the more time there is to reshape the affected hipbone. Most children with Legg-Calve-Perthes disease do well in the long run.

Signs and symptoms of Legg-Calve-Perthes disease include:

• Limping
• Pain or stiffness in the hip, groin, thigh or knee
• Limited range of motion
• Shortened leg on the affected side, in some children

In some cases, pain and stiffness get better when your child is resting, only to reappear once your child is active again.

The underlying cause of Legg-Calve-Perthes disease — also known as ischemic (avascular) necrosis of the hip — isn't clear. But what happens is this: There's a temporary loss of blood supply to the ball portion of the hip joint (femoral head). Without an adequate blood supply, the femoral head deteriorates. As dying bone cells are replaced with new cells, the bone becomes unstable, and may break easily and heal poorly.

Legg-Calve-Perthes disease can affect children of nearly any age, but it's most common among boys ages 4 to 8. In fact, it's about five times more common in boys than in girls. When girls develop Legg-Calve-Perthes disease, it tends to be more severe.

In addition, Legg-Calve-Perthes disease is most common in whites. The disease may be more likely in physically active children who are small for their age and in those who are exposed to secondhand smoke.

Talk to your child's doctor if your child:

• Begins limping
• Complains of hip, groin or knee pain

Diagnosis of Legg-Calve-Perthes disease is often based on:

• Your child's signs and symptoms
• A physical exam
• Imaging studies

Your child's doctor may recommend X-rays, magnetic resonance imaging (MRI) or bone scans to detect changes in the bones. Sometimes Legg-Calve-Perthes disease is detected incidentally during an X-ray done for other reasons.

Complications of Legg-Calve-Perthes disease may include:

• Permanent hip deformity. Legg-Calve-Perthes disease may cause a permanently deformed hip joint — especially if the condition develops after ages 6 to 8.
• Increased chance of osteoarthritis. Severe cases of Legg-Calve-Perthes disease may increase the risk of osteoarthritis as an adult.

If your child is diagnosed with Legg-Calve-Perthes disease, he or she may be referred to a pediatric orthopedic specialist for treatment.

Treatment is designed to protect the hip from further stress and injury and keep the ball of the thighbone in the hip socket. While resting the joint may help, prolonged bed rest isn't recommended. Depending on the severity of the condition, treatment options may include:

• Anti-inflammatory medications. Over-the-counter medications, such as ibuprofen (Advil, Motrin others), can help relieve pain. They can also reduce joint inflammation when used for months at a time. The dosage may be decreased as your child's hip begins to heal. Although it is an anti-inflammatory medication, aspirin isn't recommended for use in children.
• Physical therapy. Range-of-motion exercises can help maintain joint mobility. These exercises can be done at home or with the help of a physical therapist.
• Crutches. Crutches can ease pain by keeping your child's weight off his or her hip.
• Casts, braces or traction. Temporarily immobilizing the bone can help promote healing. This may be done with leg or hip casts, leg braces or traction (applying a pulling force to the bone).
• Surgery. If a groin muscle has shortened due to excessive limping, it may be surgically released from the bone. After surgery, the affected leg is put in a cast for six to eight weeks to allow the muscle to grow to a more normal length. Sometimes the hip ball must be replaced within the socket. In other cases, the hip socket is repositioned.

Legg-Calve-Perthes disease can't be prevented. But with appropriate treatment, most children can go back to normal activities within 18 months to two years.