Cracked? Well that's new to me. Usually the doughnuts compress (collapse) and protrude through the turret too far. The bearings themselves are pretty robust.
Knocking when bouncing the suspension could be the link rods that attach the struts to the anti-roll bar. Were they OK when you removed the struts? Recently renewed? Or a knock noise whilst driving could be the nearside idler arm but that's usually also associated with sloppy steering.
The drop links are brand new, fitted by myself and I double checked the tightness several times following reading posts on here! The offending bearing was found to be seperated everytime I dropped the strut. I've ordered up anotherone to eliminate the possibility of a bad bearing.
The top mounts were cracked (They were stamped with GM so I suspect they were original) and on removal found to be compressed, they were defiantley due renewal.