The suspension knuckle mounts the hub and connects the upper and lower control arms, which allows your wheel to move vertically over rough roads. If your ball joint breaks or fails, your suspension knuckle may crack. Be sure to check your suspension knuckle if you're also experiencing ball joint problems. For all of your suspension knuckle, ball joint, and suspension needs, check out O'Reilly Auto Parts. We also carry the tools needed to properly replace suspension components.