dont know if this would help i had well i think its the same this knocking noise it turned out to be a bolt that holds the cliper in place thought it could initialy be a coil had snapped or a drop arm/wishbone was worn but just a simple bolt allso stoped what sonded like my pads were rubbing on my disk dont know if this would help but this was my expirience :) (forgot to add it had fallen out and it ws the upper one of the two)