129 Shock Mount Questions-Knock when turning

[SunGuy]

'99 SL500, 53,000mi.

A knocking sound has developed recently when, for instance, backing out of a parking space and turning the wheel left or right. Same knocking sound is present also going forward...left or right turns. It's definitely coming from the front of the car, but I don't 'feel' it in the steering wheel. The under car steering elements appear to be tight with no evident slop in tie rods, center link, etc. and no fluid leak from the struts.

When checking the upper strut mounts while the car was standing still, I noticed they move, or rock, but I can't duplicate the knocking sound as when the car is moving; then I can duplicate it at will.

First question,
o are the upper mounts supposed to 'rock' as the wheels turn?

o if the answer to the above is either yes or no, is there an adjustment available to put the mount back in spec, and of course, what's the spec?

Thanks in advance for your help.

Bob