2001 Ford Taurus

About a week ago I started hearing this weird clunking noise from the back of my car. It felt as though my struts had been broken. When I went to check my car did not seem that it was sitting any lower or anything was out of the usual. I replaced my struts in July of last year. The other day the noise got pretty bad when I was turning corners. I went to look under the car and on the left side of my cars back wheel above the swing arm it looked as though this rod was missing a bolt because on the other side this specific peice had one. I cannot figure out what this piece is called or how much it will cost to fix.