What should you know about Perthes disease diagnosis?

A clinician will ask when the limp or discomfort began, whether pain is felt in the hip, groin, thigh, or knee, and whether activity changes it. They will watch the child walk and compare hip movement on both sides. Difficulty moving the hip outward or rotating it can be a useful clue, but it is not enough to confirm Perthes disease.

An X-ray is commonly used to look at the femoral head and hip socket. Early images may not show every change, so follow-up imaging or another scan can be considered when symptoms and examination remain concerning. Other causes of limping may need to be assessed too.

Keep the planned appointments, because the hip can change as the condition progresses. Follow the clinician’s instructions about weight-bearing and activities, and record episodes of pain, limping, or reduced movement. Paediatric physiotherapy may be recommended to maintain safe range of motion. If the femoral head is at risk of losing a good fit in the socket, the orthopaedic team may discuss procedures such as osteotomy.

Seek urgent care if the child cannot bear weight, has sudden severe pain, has fever with a hot or swollen hip, or seems seriously unwell. Contact the treating team sooner if the limp rapidly worsens, pain interrupts sleep, or hip movement becomes noticeably more limited. [Limping](/symptoms/limping/) provides additional symptom context.

Ask which findings support the diagnosis, whether more imaging is needed, what activity is safe, and how hip movement will be monitored. You can also ask how physiotherapy fits the plan and what changes would prompt discussion of osteotomy.