Check the bottom ball joints, i used to get knocking at slow speeds and both mine were shot to bits.
Like Cue said though there are a few things it could be.
Mine is knocking over bumps in the road on the near side front and also when braking. Have ball joint bearings and bushes ready to fit so hoping this will cure the noises.
Were any of your noises removed with new bushes / ball joints?
As far as i'm aware, new bushes and ball joints did stop the knocking, I just used standard Renault parts, not had a problem since. Jeez that was 3 and a half years ago, seems like yesterday!