Wheel Knocking

[Sycamore]

Hi All,

The rear wheel on my road bike has started making a nasty knocking sound.
I had it on the work stand last night and was trying to index the gears, but I have noticed the knocking over the last few days.

It happens both when pedalling as well as when free-wheeling. Can't seem to pin-point exactly where it is coming from, and nothing seems to be clashing/getting caught anywhere.

Have taken the wheel off and it spins freely etc.

Any ideas what's causing it?

[Roastie ITR]

Try moving the wheel side to side (left to right) whilst it is in the bike frame, it could be loose cones.