Rotors and bearings don't make knocking sounds. Bushings could depending on which ones. Common causes are worn ball joints, tie rod ends, struts, upper strut mounts, and anti-sway bar links and bushings. It's helpful to know when and under which conditions the noise occurs. Your best bet is a suspension and steering inspection at a tire and alignment shop. That is normally a part of any alignment.

Answered by caradiodoc (expert)
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