What should you know about the Perthes disease age group?

Perthes disease affects the rounded top of the thigh bone inside the hip joint. It develops during childhood, often after a child begins limping or reports hip, groin, thigh, or knee discomfort. The child’s age, the shape of the hip, how much movement is limited, and whether one or both hips are involved all help the orthopaedic team estimate how the hip may develop. A younger child may have more growth remaining, while an older child may need closer assessment of how well the femoral head stays within the socket.

Age is one part of the picture, not a diagnosis by itself. A child with a limp may have many possible causes, including problems outside the hip.

Arrange a clinical assessment if a limp persists, hip movement becomes restricted, or pain keeps returning. The clinician may examine walking, hip movement, and leg length, then decide whether imaging is needed. Until reviewed, follow advice about activity: high-impact play, running, or jumping may need to be reduced, while gentle movement may be encouraged. Paediatric physiotherapy can help preserve comfortable hip movement and support safe daily activity.

Seek urgent medical advice for a child who suddenly cannot walk or put weight through the leg, has severe pain after an injury, develops fever with a hot or swollen joint, or appears acutely unwell. A new or worsening limp without a clear injury also deserves timely assessment; see [Limping](/symptoms/limping/) for related guidance.

Ask: How does my child’s age affect the outlook? Which activities should be limited? How will hip movement be checked between visits? Would paediatric physiotherapy help? When would a procedure such as osteotomy be considered?