If the ball joint boots are torn, then grease could have leaked out and/or dirt could have gotten in.
Either way, I would first make sure that the ball joints are still structurally sound before I would be looking in to just replacing the boot (which I don't know whether or not is sold seperately).
You may have to replace the ball joints.
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record