What are the warning signs of a bad sway bar on a 1995 ford windstar?

I believe they are also called (stabilizer bar),they are behind the front tires,1 on each side of course.Usually you start hearing a knocking sound when hitting bumps.People say to exchange both at the same time but not necessary.Get them fixed asap because they wear down the connection area and you don't want them to break while driving because you could lose steering ability.

I'm weak on Ford's, but as far as I know the sway bar goes across from one wheel to the other in front of the wheels. Damage from impact or worn rubber bushings.