This is not growing pains because he has a limp, day time symptoms, restriction of range of his hip and has a low grade fever. Clearly he breaks the rules of growing pains.
Investigations need to exclude infection or even malignancy.
Blood tests are normal (complete blood count, acute phase and blood film).
Radiographs of his hips are normal.
Ultrasound of his right hip demonstrates a small effusion.
This is likely to be an irritable hip but in view of his low grade fever he is kept under observation. He is less well the next day and again has a fever. Repeat blood tests show a raised white cell count. Blood cultures from the day before are still negative. Repeat ultrasound scan again shows a collection at the right hip. He is taken to theatre, the hip irrigated and the fluid sent for culture. He is started on antibiotics on the assumption that this is septic arthritis. His CRP is raised (15mg/L) and white cells raised at 13x106/L. His fever settles and his blood tests return to normal. Subsequent blood cultures are negative. He completes his antibiotic course, along with physiotherapy and has a full recovery.
His follow up includes repeat radiograph of his hips as sometimes Perthes disease can develop after an irritable hip.