[iroc343]

You sure that's a picture of a ball Joint? Looks like a tie rod end to me. Either way, the joint pictured isn't the type that has the wear sensor in it. The ones I am familiar with have the grease zerk screwed into a nipple and you judge wear by the amount that nipple sticks out. I prefer the method described above, unload the ball joint and check for looseness by eye/feel.