This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Imaging and basics in Ohopedics, Subject name: Orthopaedics
A 10-year-old obese boy was referred to the emergency with a history of hip pain. He was observed to be limping and complained of severe pain. Which of the following investigation is not required: 
Select and explain. 
A. X-ray of the hip, B. MRI of the hip, C. CT scan of hip, D. USG of hip
C: CT scan of hip
Answer: C: CT scan of hip 
Explanation: Order of Investigations in any inflammatory Joint Swelling X-ray | MRI | Aspiration This patient is an Obese limping child with hip pain, the possible differential diagnosis would be : Osteomyelitis (X-MAS) Septic ahritis (X-MAS) Slipped capital femoral epiphysis (X-MRI) Transient synovitis (X-MAS) Hence CT will be least preferred.