2002 jeep grand Cherokee 4.7v8

Sorry if stupid question but I'm need to have them replaced and I'm pricing ball joints for the front. My question is do I need to buy a upper and lower ball joint for the front side I'm having trouble with? Or should I have the upper and lower replaced on both sides on the front?

 

You might as well do all 4. Get it all out of the way now.

 

Yea if you have the front end apart, might as well replace all of them. Id even do the tie rods while you are at it