Question category: Cardiology
A 40 year old female who is on long term steroids for Polymyalgia Rheumatica presents with sudden onset left hip pain. This is severe and she is unable to put any pressure on it. There is no history of trauma. On examination there is no obvious abnormality however there is a great reduction in left hip flexion and internal and external rotation. A hip x-ray reveals sclerosis of the femoral head. What is the most likely diagnosis?