So I'm making a fairly rigid robot where only the top most bone on the leg can rotation on Z and the everything below that can only rotate on the X, I read some other posts about not using rotation constraints but instead using the IK rotation lockers on the bone properties instead though it doesn't seem to work perfectly to how I imagine.
You can see here that the top bone which should only twist here is tilting. The other bones seem to work lock rotation perfectly.
Thanks for reading.