Knocking Sound from rear

[S3 MCW]

Last few weeks have noticed when I go around a roundabout I get a "knocking sound" from the rear drivers side. Like a thunk. Driving along straight roads ok. Quick inspection (my non-mechanic eyes) looks OK under the car. Any ideas?

 

[Dom Knight]

I get the same but I think it's on the passenger side.
I wondered if it was a shock !!!

 

[Alex C]

rear anti-roll bar bushes?

 

[Vex182]

I have a similar thing, mine is only under braking, just get this knock on the passenger rear side. I get some really small knocks too when going over really small bumpy roads, that's stuff that the S3 rides harsh over and I can not work out what it is yet.