What Causes Pain In Left Hip And Thigh?

I have had pain in my left hip. For the past 2-3 months my left hip will burn. Now the pain is bothering my left thigh as well. I am now limping. I must tell you that I had a double lung transplant 9 yrs ago. I have been on steroids for about 15 years. What do you think of the possibility of Avascular Necrosis? My PCP took an xray and said it only shows tendinitis. I am having a second opinion on Feb. 19th, but I wondered what you thought. Thank You, Sandy Ozanich