AANP Family Nurse Practitioner (FNP) Certification ExamDiagnosisMedium
A 6-year-old child presents with a 2-week history of worsening right hip pain, especially with activity, and a noticeable limp. The pain sometimes radiates to the knee. On examination, there is decreased range of motion, particularly internal rotation and abduction of the right hip. There is no history of trauma or fever. What is the most appropriate initial diagnostic study?
- AComplete blood count (CBC) with differential
- BUltrasound of the hip
- CMagnetic Resonance Imaging (MRI) of the hip
- DX-ray of the hip and pelvis
Show answer & explanationAnswer & explanation
Correct answer: D. X-ray of the hip and pelvis
The clinical picture of a young child with chronic hip pain, limp, and limited hip motion without trauma, points to conditions like Legg-Calvé-Perthes Disease (LCPD) or Slipped Capital Femoral Epiphysis (SCFE). A plain X-ray is the initial imaging study of choice for both, as it can reveal characteristic changes.
Why the other options are wrong
- A. A CBC is not the initial diagnostic study for hip pain and limp; it would be more relevant for suspected infection or inflammatory conditions, though LCPD is not primarily infectious.
- B. Ultrasound can be useful for detecting joint effusions (e.g., in transient synovitis), but it is less effective for visualizing the bony changes seen in LCPD or SCFE.
- C. MRI is a more advanced imaging study, often used after X-rays if the diagnosis remains unclear or for further characterization, but not typically the first step.
Legg-Calvé-Perthes Disease (LCPD)
A childhood hip disorder characterized by avascular necrosis of the femoral head due to temporary interruption of blood supply.
- Most common in boys aged 4-8 years.
- Presents with limp, hip or knee pain, and limited hip motion.
- Diagnosis relies on plain radiographs showing characteristic changes.
Memory trick: Kids' Limping Hips Need X-Ray Snaps.