Hilla,
This is the exact same thing that is happening to my wifes 07 SEL AWD Fusion 70,000 miles. I took it in to the mechanic after looking for all of the obvious things that could be wrong.
The mechanic said that the lower ball joints were squeaking but nothing was loose and nothing needed to be replaced, as long as im ok with the nasty squeak. He said if i wanted to replace it would be about 125 for each ball joint. Hope this helps.