This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolic Disorders of Bone, Subject name: Orthopaedics
A pregnant women present with 6 week history of right hip pain.On exam she has guarding on passive hip movements.Plain x ray showed osteoporosis of proximal femur.Most likely diagnosis is? 
Select and explain. 
A. Acute chondrolysis of pregnancy, B. Avascular necrosis of femoral head, C. Transient osteoporosis, D. Septic ahritis
C: Transient osteoporosis
Answer: C: Transient osteoporosis 
Explanation: Transient osteoporosis occur in the pregnancy which is the cause here. Septic ahritis does not lead to osteoporosis and no local or systemic symptoms of infection are present in the patient. Patients with AVN of the femoral head often repo groin or anterior thigh pain that is exacerbated by weight bearing.Avascular necrosis (AVN) may be asymptomatic in some cases. Acute chondrolysis of pregnancy is a rare entity with/without any radiographical changes.oftenly its a diagnosis of exclusion