No one (or very few, to be technically correct) replace just the ball joints because of the cost benefit ratio. A good ball joint is 35 + shipping (Or tax. Or tax & shipping). It's much easier to r&r it if you take the arm off the car. 15 more dollars gets you the entire arm. Since you probably had the arm off to begin with for the ball joint replacement, why even bother? A new arm will get you the new bushings for the frame end too.