I had a knocking noise coming from the rear n/s when going over rough roads in my recently purchased is200 with 79k, took it to a garage and asked them to check the shocks and they said they couldn't see anything wrong with them and no signs of them leaking etc, not convinced with there verdict I rang the previous owner and asked him if the shocks had ever been replaced by him which he replied no, after searching on here for hours I decided that due to the mileage to change them anyway and ordered a full set of kyb shocks and had them fitted, hey presto!! no more knocking!! turns out that both front and rear n/s shocks were shot, not saying that this is what anyone elses knocking problem is but generally I think if your mileage is fairly high and your on the originals get them checked properly by removing them from the car.