the key items on the control arm are the 2 bushings that hold it to the frame and the ball joint. The ball joint is what goes bad first. This joint pretty much takes most all the movement for the bottom of the suspension on each side. As they become worn, the front suspension feels looser and a little less control. Also with this comes a knocking sound when you turn at low speeds or going over bumps (not to be confused with the knocking from bad strut mounts). You replace the whole control arm as a unit and it is fairly simple if you have a ball joint and tie rod fork. Might want to think about replacing the tie rod ends while you are there...another joint that goes around 80K - 100K miles. Suggestion is to avoid scan tech and go with OEM as it will last longer.