Originally Posted by sortedcossie.com
i've always changed the ball joint on my cars as if the rubber has perished/split then good chance the joint itself may not be in ace condition - i've had a ball joint break and i'll not risk it now.
obviously, if the joint is newish and the rubber has split through being pinched then its prob worth just getting a replacement rubber.
As you said its some times best to replace the whole lot, saves messing around when you find out the joint is knackered because all the grease has gone or shit has got in there.