IK constraint causes crazy global rotation I was following a rigging tutorial (first minutes of third video) on a simple model I made earlier. But when I add an IK constraint on the bone shin.L to have the bone foot_IK.L become an IK controller, it gives very odd behavior.

When moving the foot around in Pose mode for a small amount, the IK seems to work fine, but when you move it further, the rotations go berserk. And even if i return the mouse back to where it started, the rotations keep being all messed up.

https://www.dropbox.com/s/ikrqtk7kh164c22/dusty_05_foot_bones_added.zip?dl=0

What did I do wrong?
Here is what I would say:


Select your armature, go in Properties > Data > Display > B-Bone, so that you can easily see your bones. Select all the bones in Edit mode and ctrl alt S to thin them.
In Edit mode, select the foot_IK.L and drag it back behind the foot so that you can see it. Also, rotate it 180° on the X axis so that its head is in the good position.
Now, the parentage is bad, neither the foot.L nor the foot_IK.L should be parented to the shin, and the foot.L should be parented to the foot_IK.L, so, in Edit mode: Select the foot_IK.L and alt P > Clear Parent and select the foot.L then select the foot_IK.L and ctrl P > Make Parent > Keep Offset.


It should work correctly.