What should you know about Perthes disease X-ray?

Perthes disease affects the ball at the top of the thigh bone while it is still developing. On an X-ray, the clinician looks at whether the ball is centred in the socket, whether its outline remains rounded, and whether there are changes in density, height, or fragmentation as the condition progresses and repairs.

An X-ray is one part of the assessment. The clinician also considers age, hip movement, pain, walking pattern, and the child’s examination. An early X-ray can be less clear than a later image, so a normal or subtle first image does not always settle the question. Further imaging may be suggested when the examination and X-ray do not match.

Tell the imaging team if your child may be pregnant, although this is uncommon in young children, and mention any difficulty staying still. The child may need to lie in more than one position so both hips can be compared. The test is quick, but positioning can feel uncomfortable when the hip is sore.

Bring previous images or reports if they were taken elsewhere. Keep the follow-up appointment even if symptoms improve, because repeat images help show the direction of healing and whether the hip remains well positioned. Follow advice about activity and exercises while the orthopaedic team reviews the findings.

Do not wait for a planned X-ray review if your child suddenly cannot bear weight, has severe or rapidly increasing hip pain, or develops marked swelling, fever, or an unwell appearance. Seek urgent help as well for a foot that becomes cold, pale, blue, or numb.

Arrange clinical review for a persistent limp, increasing stiffness, night pain, or pain that limits ordinary play. Limping is a symptom with several possible causes; an X-ray result must be interpreted with the child’s history and examination.

Ask: What changes do you see in the hip ball and socket? Is the ball still centred? Does this image suggest an early, active, or healing phase? When should the next examination or X-ray take place? What movement and activities are suitable now, and would another scan add useful information?