Question:medium
A 6 year old child presents with pain in the hip in the femoral triangle region and limitation of movements. X-ray does not reveal any abnormality. What is the next step?
A 6 year old child presents with pain in the hip in the femoral triangle region and limitation of movements. X-ray does not reveal any abnormality. What is the next step?
Show Hint
Early Perthes disease can have a normal X-ray; pick the most sensitive imaging for avascular necrosis.
Updated On: Jun 24, 2026
- USG
- MRI
- Aspiration
- Traction
Show Solution
The Correct Option is B
Solution and Explanation
A boy of 6 years with groin pain in the femoral triangle and a stiff, painful hip, in whom the radiograph shows nothing, fits Perthes disease, which is osteonecrosis of the capital femoral epiphysis of unknown cause in this age group.
The trap in the question is the normal X-ray. Radiographic signs of Perthes disease ($\textit{e.g.}$ a smaller, denser epiphysis followed by the subchondral crescent and fragmentation) lag behind the actual loss of blood supply, so an early film can look completely normal even when the head is already ischaemic.
When you need to see ischaemia or marrow change that the X-ray cannot show, the right tool is magnetic resonance imaging. MRI picks up the avascular and early necrotic changes well before bony collapse and so confirms the diagnosis at the earliest stage.
The remaining choices do not solve the diagnostic problem: ultrasound merely demonstrates fluid in the joint, aspiration is for ruling out joint infection, and traction is a management measure rather than an investigation.
Hence the appropriate next step is MRI.
\[\boxed{\text{MRI}}\]
The trap in the question is the normal X-ray. Radiographic signs of Perthes disease ($\textit{e.g.}$ a smaller, denser epiphysis followed by the subchondral crescent and fragmentation) lag behind the actual loss of blood supply, so an early film can look completely normal even when the head is already ischaemic.
When you need to see ischaemia or marrow change that the X-ray cannot show, the right tool is magnetic resonance imaging. MRI picks up the avascular and early necrotic changes well before bony collapse and so confirms the diagnosis at the earliest stage.
The remaining choices do not solve the diagnostic problem: ultrasound merely demonstrates fluid in the joint, aspiration is for ruling out joint infection, and traction is a management measure rather than an investigation.
Hence the appropriate next step is MRI.
\[\boxed{\text{MRI}}\]
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