A car's independent suspension is made up of many different components. If any of these components become bent in an accident or worn out from use, the suspension may not perform as well as it normally does. Control arms are one of the components that connect the hub to the chassis. If these parts become bent or the bushings in them become worn, the result can be shaking, vibrating and loose steering.
Test drive the car on the freeway. Torn and worn out control arms or bent control arms will cause a car's steering to vibrate. This is a symptom that will become exacerbated the higher the speeds are and may become very noticeable at freeway speeds. Other potential causes of this symptom can be a bad alignment, bent wheels or unevenly worn tires.
Test the brakes. If the steering wheel shakes when you apply the brakes, the control arm bushings may be worn or the arms themselves may be bent. This can also be caused by bent wheels and warped brake rotors, though.
Drive the vehicle around a series or corners and also pay attention to how it behaves in a straight line. Bad control arm bushings can make the steering feel loose and imprecise, and can also cause the vehicle to wander back and forth in a straight line from the excessive slop of the worn bushing.
Determine if the wheel moves excessively. Jack the car up with a floor jack so that the wheel is fully suspended in the air. Place a hand on either side of the tire and attempt to move the wheel. If you feel the wheel and the suspension move easily, the control arms or control arm bushings may be bad.
Listen for noise while driving. Worn-out bushings can cause the control arms to rattle and clunk while you're driving around corners -- a symptom that may be more noticeable at lower speeds.