The blood flow to the femur is interrupted, and the tip of the bone dies over a period of one to three weeks. The disorder causes a flattening of the top of the femur (the ball of the head of the femur). Usually just one hip is affected, although it's possible for both to develop the condition.

A new blood supply causes new bone cells to appear in the region over the next 6 to 12 months. New bone then replaces the old bone within 2 to 3 years.

Legg-Calve-Perthes disease occurs most frequently in boys 4 to 10 years old. Recent research shows that this disorder may reflect subtle disorders of blood clotting.

• Knee pain (may be the only symptom, initially)
• Persistent thigh or groin pain
• Atrophy (wasting) of muscles in the upper thigh
• Slight shortening of the leg, or legs of unequal length
• Hip stiffness restricting movement in the hip
• Difficulty walking, walking with a limp (which is often painless)
• Limited range of motion

During a physical examination, the doctor will look for a loss in hip motion. A hip X-ray or pelvis X-ray may show signs of Legg-Calve-Perthes disease.

The aim of treatment is to protect the bone and joint from further stress and injury while the healing process takes place. Bedrest or crutches may be needed during the initial phase. A brace, cast, or splint to immobilize the hip's position may be used while bone regrowth takes place. Surgery may be performed to keep the hip in its socket.

The outcome is usually good with treatment. Most bone will heal with minimal lasting deformity.