L300 knocking

Hi there,

My 2003 Saturn LS L300 is making a knocking noise when I accelerate or turn corners. It's when I turn either way, not just one direction. It seems to be getting worse, and it seems to go away once my car temp is up. My check engine light came on shortly before this and when I took it to get the computer read it gave me the code for Heat/Oxygen sensor. Could these be related? Any idea what the knocking is? I plan on taking it in to the shop I just want to know what I'm looking at here and how much I will have to spend. My car has 64,000 miles.