What Causes Pain In The Thigh Post Hip Replacement Surgery?

My husband had total hip replacement on his left hip on Jan 8 2015 post operative all went well started physical therapy two weeks ago...in 2010 he had hip replacement on right side all went well no problems...in the last week he has been having increased pain in his upper right thigh what could be causing that.. He went to the surgeon of the recent surgery and was given a shot for possible inflammation. He was advised ifpain does not subside he will have to have a bones scan .