There are quite a few suspension bushes that it could be. Best thing to do is jack it up. Support it safely and then grab hold of the wheel top to bottom and then at 8 oclock and give it a good waggling (if thats the correct term!) and check for excess play.
You can also use a lever bar inbetween the joints to check for play as well.
It could be something as cheap and simple to fix as an anti rollbar link or it could be the bottom ball joint as you say but either way it wont cost you a fortune to fix if it is just a bush.