Why have you got rear wheel knocking noise after bearings changed?

Why have you got rear wheel knocking noise after bearings changed?
It could be several things, your bearings could be under a pre load, which means there is exesive pressure on them caused by them being over tightend, it could also be as simple as a brake hanging up on the drum or disk. you may have a bent rim possibly but that would cause the car to vibrate. Also you may have a worn spindal, the shaft that the bearings slide onto. You could possibly have a brearing catching or binding up. I would definitely have it looked at so you don't have a bearing go out because it could mean you lose you tire completely.