Perthes disease can be divided into different stages that describe the course of the disease:

1. Initial stage:
   The femoral head loses stability due to the reduced blood supply.
2. Fragmentation stage:
   The dead bone disintegrates, and the femoral head becomes deformed.
3. Reparative stage:
   New bone tissue begins to form, but the shape of the femoral head often remains altered.
4. Final stage:
   Bone remodeling is complete, and the femoral head may be deformed, leading to permanent limitations.

The exact cause of Perthes disease is not fully known; however, several factors play a role:

• Circulatory disorders:
  • A disrupted blood supply to the femoral head is the main trigger.
• Genetic predisposition:
  • In some cases, there is a familial clustering of the disease.
• Trauma:
  • Minor injuries can impair the blood supply to the femoral head.
• Risk factors:
  • Passive smoking, malnutrition, and hormonal influences during the growth phase.

The symptoms of Perthes disease often develop gradually and vary depending on the stage of the disease:

• Pain:
  Pain in the hip that often radiates to the thigh or the knee.
• Movement limitations:
  Difficulty with rotating, extending, or bending the hip joint.
• Protective limp:
  A typical limp, especially after exertion.
• Muscle atrophy:
  Decrease in muscle mass in the thigh due to limited movement.
• Leg length discrepancy:
  In advanced stages, the affected leg may appear shortened.

Diagnosis is made through a thorough medical history, clinical examination, and imaging procedures:

• Medical history:
  • The physician asks about pain, mobility limitations, and family history.
• Physical examination:
  • Assessment of range of motion and tenderness in the hip area.
• Imaging procedures:
  • X-ray: Shows typical changes of the femoral head in the different stages.
  • MRI: Detailed depiction of blood supply and early stages of the disease.
  • Ultrasound: Supplementary examination if fluid accumulation in the joint is suspected.

Conservative therapy

The treatment aims to relieve pressure on the femoral head and promote regeneration:

• Offloading the hip joint:
  • Use of walking aids or orthoses to protect the joint.
• Physiotherapy:
  • Exercises to improve mobility and strengthen the muscles.
• Pharmacological therapy:
  • NSAIDs for pain relief and reduction of inflammation.

Surgical therapy

In severe cases or with pronounced deformities, surgery may be necessary:

• Realignment osteotomy:
  • Correction of the leg axis to better center the femoral head in the acetabulum.
• Femoral or pelvic osteotomy:
  • Adjustment of the bone structure to promote healing.
• Endoprosthetics:
  • Joint replacement in rare cases of irreversible damage.

Since the exact causes are not fully known, there are no specific preventive measures. General recommendations include:

1. Regular exercise: Promoting joint health through age-appropriate activities.
2. Reduce risk factors: Avoiding secondhand smoke and promoting a balanced diet.
3. Early detection: At the first signs such as hip pain or limping, early medical evaluation.
4. Adjust load: Reducing intense physical activities during growth phases.