yes they have been done apart from the 1 under the body but that looks like new not 1 crack or split
??? One under the body ???
Are we talking about the same thing here, the droplinks sit between the Anti Roll Bar (ARB) and the lower arm. 1 each side.
If the droplink bushes are worn, you will get knocking as you go over bumps etc.
Other things to check are the lower suspension arms, make sure the bolts holding them on are tight, and the bushes aren't worn.
Track rod ends, make sure there is no movement.
also check that the suspension strut top bolt is not loose, along with the mounting bolts.
Is the knocking continual. ie rythmic and increases with speed ?
If so then something that is turning is causing the knock.
Could be a loose bolt on the inner CV joint, that is catching on something,
It could also be brake related.
best to get it on axle stands then see if you can locate the knocking