This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: TB of the Hip, Knee, Other Joints, Subject name: Orthopaedics
[{'content': 'A 30-year-old male HIV positive on antiretroviral therapy has pain in right hip region. Flexion, abduction and external rotation deformity of right hip for 2 months, what is the most likely diagnosis? \nSelect and explain. \nA. Avascular necrosis, B. TB hip, C. Transient synovitis, D. Septic arthritis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: (b) TB hip in HIVAVN hip in HIVIncidenceMore CommonLess CommonDeformityFABER-stage of synovitis may be prolonged on treatment, then subsequently with onset of arthritis - FADIRLimitation of abduction and internal rotation so initially position is adduction and external rotation (opposite to movements limited) and than subsequently with onset of arthritis FADIR Unilateral (usually)Bilateral (usually)', 'role': 'assistant'}]