What would cause a knocking sound after having lower control arm replaced?

I had the same issue, the solution I found was: Bolts weren't torque to spec. So there are 3 body bolts and 1 ball joint bolt. Chances are, if it's like a creaking/cracking/popping sound- like an old wooden chair, it's the body/frame bolts. Solution: Looking at the control arm you should be able to tighten the 2 on the rear side for both driver/passenger without lifting the vehicle. The bolt by itself on the body, it's recommended to have the vehicle up in the air but have the suspension at ride height. [this can be done by get it up enough you can get under easy, and then carefully lifting the suspension to ride height via lifting it from the ball joint area] {DO NOT TORQUE THE SOLO BOLT WITH SUSPENSION AT FULL TRAVEL/HANGING it was cause premature wear} Mazda spec's:"The left side control arm frame fastener gets tightened down to 175 ft-lbs. The right side fasteners can both be tightened down to 120 ft-lbs." TL:DR Try torquing the 3 frame bolts (preferably with the car in the air, with suspension at ride height.) Left frame bolt is 175 ft-lbs Right frame bolts are 120 ft-lbs Lower ball joint is 30 ft-lbs [Personal, not sure which are considered right/left cause it depends on which way you're looking at them. But I assume the 175 ft-lbs are for the 2 close together and the 120 ft-lbs are for the solo one] {https://autospecz.com/mazda/cars/2016/mazda32.0/torque-specs_front.php}