What is "steering knuckle"

thumb|right|300px|Double Wishbone Suspension In automotive suspension, a steering knuckle is that part which contains the wheel hub or spindle, and attaches to the suspension components. It is variously called a steering knuckle, spindle, upright or hub, as well.

The wheel and tire assembly attach to the hub or spindle of the knuckle where the tire/wheel rotates while being held in a stable plane of motion by the knuckle/suspension assembly.

In the attached photograph of a double-wishbone suspension, the knuckle is shown attached to the upper control arm at the top and the lower control arm at the bottom. The wheel assembly is shown attached to the knuckle at its center point. Note the arm of the knuckle that sticks out, to which the steering mechanism attaches to turn the knuckle and wheel assembly.